Talk - Infn

ggi.fi.infn.it

Talk - Infn

Supersymmetry searches

with the ATLAS detector

T. Lari

INFN Milano

On behalf of the ATLAS collaboration

Thursday, November 10, 11

1


! Scalar"quarks"(squarks)"and"leptons"(sleptons)"

! Spin"½"partners"of"gauge"bosons"(winos,"zinos,"gluinos)"

! Needs"an"enlarged"Higgs"sector"as"well"

What we are looking for

! Three"neutral"(h,"A,"H)"and"two"charged"(H ± )"Higgs"bosons" @*V$'I8.H)0'*T$'J%%*(+J$+*O0(8.P$

Abstruse

! And"the"associated"spin"½"partners"(higgsinos)"


Thursday, November 10, 11

What we are looking for

For ATLAS, first priority is to discover any signal we are sensitive to

Look into all final states where there might be something.

Do not tune cuts on any gluino particular masses below simulated 2 TeV, signal, rising but to 1075 try to GeV have if the complementary squarks signal

selections which are sensitive and gluinos to the are various assumedpossibilities to be mass-degenerate. (short or long These decay limits chains, small

or large mass splittings, remain etc.) essentially unchanged if the ˜χ 0 1 mass is raised as high

We are always open to i.e. suggestions CMSSM/MSUGRA for promising with tan signatures β = 10, we A 0 = are 0, overlooking! µ>0, the (but be

patient, it might take limit a while on mbefore 1/2 reaches we come 460 GeV back for with lowresults)

values of m 0 ,andequal

In case of negative results, we place exclusion limits in various forms

mass squarks and gluinos are excluded below 950 GeV. The use

of signal selections sensitive to larger jet multiplicities thanin

[5] has improved the ATLAS reach at large m 0 . The five sig-

On cross section times nal acceptance regions aretimes used to selection set limitsefficiency on σ new = ( σAɛ, ). fornon-SM Model independent

but need a detector simulation cross-sections for (σ)forwhichATLAShasanacceptanceA comparison with model predictions and a

On constrained models, like mSUGRA

SUSY particles on their decay chains. In regions of parameter

space with small mass splittings between states, the modelling

of initial state radiation can affect the signal significance. This

modelling is taken from HERWIG without modification.

In the limit of light neutralinos, with the assumption that the

coloured sparticles are directly produced and decay directly to

jets and ˜χ 0 1,thelimitsonthegluinoandsquarkmassesareapproximately

700 GeV and 875 GeV respectively for squark or

as 200 GeV. In the case of a specific SUSY-breaking scenario,

detection efficiency of ɛ [44]. The excluded values of σ new are

22 fb, 25 fb, 429 fb, 27 fb and 17 fb, respectively, at the 95%

confidence level.

On particles masses for toy models with the most relevant particles and decays for that

channel, and on production cross section as a function of the particle masses

8. Summary

This Letter reports a search for new physics in final states

containing high-p T jets, missing transverse momentum and no

electrons or muons with p T > 20 GeV. Data recorded by the

MPO CR and

and Lundbeck

Union; IN2P3

gia; BMBF, D

GSRT, Greece

ter, Israel; INF

rocco; FOM a

Poland; GRIC

mania; MES

JINR; MSTD

Slovenia; DST

Wallenberg Fo

Bern and Gen

STFC, the Ro

dom; DOE and

The crucial

acknowledged

ATLAS Tier-1

mark, Norway

(Germany), IN

(Spain), ASGC

the Tier-2 faci

References

[1] L.R. Evans

JINST 3 (20 3


Our data

Results presented here are based on either the full 2010 dataset (35 pb -1 after data quality

selections) or up to 1.3 fb -1 of 2011 data.

Analysis of the full 2011 dataset (~5 fb -1 ) in progress - stay tuned!

Thursday, November 10, 11

4


Jets+E T

Miss

+X searches

The first searches have been focused on the strong production

of first generation squarks and gluinos: highest cross section

process at LHC, sensitivity well beyond Tevatron limits

already with 35 pb -1

If R-parity conservation, signature is jets+ET Miss +”X”, where

X depends on the mass spectrum and available decays

ut the rest?

Each X defines a search channel

10

1

10 -1

10 -2

tot

[pb]: pp SUSY

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EtMiss+bjets+0lepton

EtMiss+bjets+1lepton

EtMiss+2 photons

10 -3

˜ e˜e*

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100 200 300 400 500 600 700 800 900

m average

[GeV]

Thursday, November 10, 11

5


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Thursday, November 10, 11

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S/B enhancement

> 1100

irection points to the primary .&&

6+P.($+.Q1.'(.0

120 background estimates

119

are and adistance∆R

consistent modelling

2A,"B%*)C+DE.FG forsystematics, = √ with p

(∆η)

all processes, are taking reduced 2 + (∆φ)

into in account the 2 TFs. = 0.2

bothThe ofanelectronisdiscarded:

taking theninto anyaccount electron bothor SMmuon and potential candidate SUSYremaining within

SMcombined and potential fit across SUSY all regions ensures

119 and modelling systematics, are reduced in the TFs. The combined fit across all regions ensures that the

121

the highest summed track p 2 signal

T ,

contamination R. $)&(5 $.".'(%)* in the CRs. %*+/ .&&

6+P.($+.Q1.'(.0 ∆φ(jet

R. $)&(5 $.".'(%)* %*+/

120 background estimates are consistent 2A,"B%*)C+DE.FG

/ for .&& )- all / processes, V6 $.".'(%)* taking into account both SM and potentia

.&&

6+P.($+.Q1.'(.0

120 background estimates are consistent 2A,"B%*)C+DE.FG for all processes,

122 TheTable irreducible 1: Criteria

121

signal contamination in the CRs. physics signal for background contamination

definition

admissionfrom to each inZ the ⇥

CRs.

/ the ¯+jets fiveevents overlapping is estimated signalregions using/ control regions

of the ATLAS detector. Only enriched(m in eff

a, Erelated T

miss and process p T inwith GeV). similar All variables kinematics: are events defined

&)- with 3%,3ANCM")WALC+/#$$.$ .&& )- / V6 $.".'(%)*

121

m eff = scalar sum of E

Miss

123

T and

adistance∆R

the

122 Thepirreducible T of 2/3/4 .&&

= )- / 0.4ofanysurvivingjetcandidateisdiscarded.

tween

physics highest V6 $.".'(%)*

The irreducible physics background from Z ⇥ ¯+jets events is estimated

background p T jets

using

from depending

Section isolated control

Z ⇥4. photons regions

¯+jets on

m eff

and

the events jets

SR.

(control isFor estimated the high usingup control to

122

regions

sverse momenta p T > 20 GeV

defined denoted mass

with ‘CR1’). a variable The reconstructed number of jets, momentum appropriate of


the .Q1")%(

photon each 0.1.*0.*'. signal is added region. %*+2AH

to the&)- InSthe

⇤P S

856

TX miss 3%,3ANCM")WALC+/#$$.$

124

123

SR,

enriched in a related process with similar

enriched all Next, jets

kinematics:

in

all with a events

related &)- pcandidates T >

with 3%,3ANCM")WALC+/#$$.$

process 40 GeV

isolated

with

with and

photons

similar

|η| < > 2.8 kinematics:

2.8arediscarded.Thereafter,

used.

jets (control

events with

78 C

vector isolated to photons and jets

123

obtain an high estimate mass selection, of the ET miss

125

regionsall denoted observed jets with ‘CR1’). inp Z T > ⇥40 The ¯+jets GeV reconstructed are events. usedControl tomomentum compute regions the ofenriched

the m in Z ⇥

eff

S S

.Q1")%(

photon

0.1.*0.*'.

is added

%*+2AH

to the ⇤P

4% of the data used, a tempo- 126 ee/µµ+jets events are used to cross check the photon + jets results and are found to be in good agreement,

856

TX miss

124 the electron, muon and jet candidates

regions denoted ‘CR1’). The reconstructed momentum of S S surviving this procedure

quirem

78 C

v

obtain an estimate

the.Q1")%( photon

of the0.1.*0.*'. ET miss is added

125

observed %*+2AH

to the ⇤P

in 856

T

ZX miss

124

78 ⇥C

vector to

are considered as “reconstructed”, and the ¯+jets term events. “candidate” Control regions is enriched

reduce

!"#$%&'()#"*$+'+)$+","-

obtain an estimate of the E miss value used in the final cut. The ∆φ cut is only applied up to the third leading

T

observed in Z ⇥ ¯+jets events. Control regions enriched in Z ⇥

S

S

S

S

S

=.,%)*+!

2A$HB#-I 856 C+DE.FG

S

S

=.,%)*+!

S

S

2A$HB#-I 856 C+DE.FG

S

=.,%)*+!

!"#$$%&%'#(%)*+)&+$%,*#"+-.,%)*$+#"/

S

S

7


surviving this procedure

reduce the background from multi-jet is

reduce the background processes.

from multi-jet processes.

the term “candidate” is

Z( )+jets CR1

gamma+jets selection

E T

Miss

+(≥2-4)jets+0 leptons

5. 5. Backgrounds, Simulation 5. 5. Backgrounds, and Normalisation

Simulation and Normalisation

background estimate

Standard Model background Standard processes Model contribute background to to the processes contribute to to the

described event counts above, in in events the signal event regions. counts The in dominant the signal sources regions. are:

The dominant sources are:

ons es W+jets, are or or reconstructed muons Z+jets, withpusing p T top T >

the pair, anti-k W+jets, single t clustering top, Z+jets, andal-

top multi-jet pair, single produc-

top, and multi-jet produc-

[9, tion. 10] criteria with Non-collision adesigned distance to parameter tobackgrounds tion. of 0.4. Non-collision have The been inputs

found backgrounds to tobe be neg-

have been foundtotobe be negligible.

clusters W+jets The of background calorime- E majorityof isof composed the miss

W+jets of

of backgroundisis composedof

of

on nlgorithm ligible. backgrounds are The three-dimensional majority (seee.g. of of the [11] seeded by those with energy significantly above

ary W vertex →τν τνis is events, associated or or W → eν,µν W → τν τν events, in in which or or Wno no → electron eν,µν events or or in in whichno no electronor

or

sured noise. Jet momenta are constructed by performur-vector

muon sum candidate over these is is reconstructed. cell clusters, muon treating candidate The largest each is isas

reconstructed. partof of the Z+jets

The largest partof of the Z+jets

over )four-vectorwithzeromass. background the (m˜g , m˜q , m˜q comes )-plane,

fromThesejetsarecorrected

the background irreducible comes component from the in in irreducible which

componentinin which

arks ffects Z →typically ofν calorimeter ν ν decays generate

non-compensation generate Zlarge →ν ν E and ν miss

decays . inhomo-

. Hadronic generate ττ decays large Ein

in

miss .. Hadronicττ decaysinin

Z( )+jets CR2

T T

Z(ll)+jets selection

s by using p T and η-dependent calibration factors based

te Carlo (MC) and validated2

2with extensive test-beam

ision-data studies [12]. Furthermore, the reconstructed

dified such that the jet direction points to the primary

efined as the vertex with the highest summed track p 2 T ,

f the geometrical centre of the ATLAS detector. Only

dates with corrected transverse momenta p T > 20 GeV

equently retained. For 84% of the data used, a tempotronics

failure in the LAr barrel calorimeter created a

ion in the second and third longitudinal layers, approxtt

CR

1.4 × 0.2 in∆η × ∆φ, inwhichonaverage30%ofthe

semileptonic ttbar

jet energy candidates is lost. The impact on the reconstructioneffor

p T > 20 GeV jets is found to be negligible. If any

ur leading jets fall into this region the event is rejected,

Thursday, November 10, 11

Signal Region ≥ 2-jet ≥ 3-jet ≥ 4-jet High

T

> 130 > 130 > 130 >

Leading jet p T > 130 > 130 > 130 >

Second jet p T > 40 > 40 > 40 >

Third jet p T – > 40 > 40 >

Fourth jet p T – – > 40 >

multi-jet CR

(E

Miss T ,jets) T T cut

reversed

W+jets CR

1-lepton W+jets

candidates

∆φ(jet, ⃗P miss

T

) min > 0.4 > 0.4 > 0.4 >

E miss

Five control regions (CR) are defined for each SR, each targeting a

specific background source.

T

/m eff > 0.3 > 0.25 > 0.25 >

m eff > 1000 > 1000 > 500/1000 > 1

The SR backgrounds are obtained from a likelihood fit to CR data,

(m

extrapolating to the SR eff , E

using

T

miss

MonteCarlo for W+jets, Z+jets, and top

pair production.

Table 1: Criteria for admission to each of the five overlapping signal

and p T in GeV). All variables are defined in Section 4. The

defined with a variable number of jets, appropriate to each signal region

high mass selection, all jets with p T > 40 GeV are used to compute

value used in the final cut. The ∆φ cut is only applied up to the third

For multijet, the expected jet. ratio between SR and CR is obtained

entirely from data, smearing a low ETMiss sample with jet response

functions obtained with measurements on multi-jet data.

at least one jet in their decays, for instance through

q ˜χ 0 1,whilegluinostypicallygenerateatleasttwo,forin

through ˜g → q q ˜χ 0 1.Processescontributingto˜q˜q, ˜q˜g and

nal states therefore lead to events containing at least two 8

For limits, signal contamination in the CR is taken into account


E T

Miss

+(≥2-4)jets+0 leptons

results

Effective mass distributions after all other cuts. The arrows indicate the final cuts.

Process

≥ 2-jet

≥ 3-jet

Signal Region

≥ 4-jet,

m eff > 500 GeV

≥ 4-jet,

m eff > 1000 GeV

High mass

Z/γ+jets 32.3 ± 2.6 ± 6.9 25.5 ± 2.6 ± 4.9 209 ± 9 ± 38 16.2 ± 2.2 ± 3.7 3.3 ± 1.0 ± 1.3

W+jets 26.4 ± 4.0 ± 6.7 22.6 ± 3.5 ± 5.6 349 ± 30 ± 122 13.0 ± 2.2 ± 4.7 2.1 ± 0.8 ± 1.1

t t+ single top 3.4 ± 1.6 ± 1.6 5.9 ± 2.0 ± 2.2 425 ± 39 ± 84 4.0 ± 1.3 ± 2.0 5.7 ± 1.8 ± 1.9

QCD multi-jet 0.22 ± 0.06 ± 0.24 0.92 ± 0.12 ± 0.46 34 ± 2 ± 29 0.73 ± 0.14 ± 0.50 2.10 ± 0.37 ± 0.82

Total 62.4 ± 4.4 ± 9.3 54.9 ± 3.9 ± 7.1 1015 ± 41 ± 144 33.9 ± 2.9 ± 6.2 13.1 ± 1.9 ± 2.5

Data 58 59 1118 40 18

Good agreement between data and SM expectation in all signal

Table 2: Fitted background components in each SR, compared with the number of events observed in data. The Z/γ+jets background is constrained with control

regions CR1a and CR1b, the QCD multi-jet, W and top quark backgrounds by control regions CR2, CR3 and CR4, respectively. Ineachcasethefirst(second)

quoted uncertainty regions is statistical (systematic). Background components are partially correlated and hence the uncertainties (statistical and systematic) on the total

background estimates do not equal the quadrature sums of the uncertainties on the components.

Thursday, November 10, 11

9


combined effects of in-time and the observed numbers of signal events with those expected from

nergy scale are accounted forby SM background plus SUSY signal processes, taking into account

uncertainties in the expectation including those which are

E

Miss T +(≥2-4)jets+0 leptons

ematic uncertainty of up to 7%

eseuncertaintiesarepropagated correlated between signal and background (for instance jet energy

scale uncertainties). The impact of SUSY signal contam-

interpretation

e impact of in-time pile-up on

as also investigated and found ination of the control regions is taken into account by applying

For limits, the SR with the best expected sensitivity is used for each signal point

ven the high energies of the jets MC-derived model dependent correction factors ∼ 0.97–1.02

to the resulting exclusion significance values. The excludedregions

are obtained using the CL s prescription [41].

certainty in MC predictions for

egions arises from the treatment An interpretation of the results is presented in Figure 2 (left)

he calculation of m eff . In order as a 95% confidence exclusion region in the (m˜g , m˜q )-plane for

ain backgrounds are estimated asimplifiedsetofSUSYmodelswithm( ˜χ 0 1) = 0. In these

LPGEN rather than MC@NLO for t t models the gluino mass and the masses of the squarks of the

tiplicity (ALPGEN processes with first two generations are set to the values shown in the figure.

All other supersymmetric particles, including the squarks

rtons for W/Z+jets production).

and factorisation scale variations of the third generation, are decoupled by being given masses

studied. Differences in the abbers

of events in the SR and CR m( ˜χ 0 1)iscomparabletothesquarkorgluinomass. ISASUSY

of 5 TeV. The limits are reduced by decay chain kinematics if

for specific processes; the imansfer

factors is, however, much and to guarantee consistent electroweak symmetry breaking.

from ISAJET [42] v7.80 is used to calculate the decay tables,

Simplified model with a gluino, first two

nnel dependent).

The results are mSUGRA/CMSSM also interpreted in with the tan β =0,A=0,m>0 = 10, A

generation squarks, and massless neutralino

0 = 0,

sidered, ~ ~

m(g)

~ ~

= m(q) > 950 GeV

m(g) >

for

700

specific

GeV m(q)

processes,

> 875 GeV

µ > 0sliceofMSUGRA/CMSSM 2 [43] in Figure 2 (right).

ton ~ ~

m(g) and lepton = m(q) trigger > 1075 efficiency, GeV These limits include the effects of the mass spectrum of the

gy scale and resolution (CR1a,

eto efficiency (CR3 and CR4),

Thursday, November 10, 11

2

10


issing transous

ATLAS

Trigger-driven

k t jet clusterhe

inputs to

7] seeded by

ed noise. Jet

tor sum over

reating each

jets are coration

and in-

B

ration factors

with extenly

jet candined.

During A

re in the LAr

region in the

1.4 ⇥ 0.2 in

jet energy is

T > 20 GeV

response for

ue to this ex-

S/B discrimination

number of jets

T

ing heavy flavour quarks is required, either to make measurements

in control regions or for cross checks, a tagging algorithm

exploiting both impact parameter and secondary vertex

information is used [19].

Electron candidates are required to have p T > 20 GeV and |⌘|

< 2.47, to pass the ‘medium’ electron shower shape and track

selection criteria Signalof region Ref. [20], 7j55 and to8j55 be outside 6j80 problematic 7j80

regions

{

of the

Jet p

calorimeter. Muon

T > 55 GeV

candidates are

> 80

required

GeV

to

have p T > 10 GeV and |⌘| < 2.4. 2

Jet |⌘| < 2.8

The measurement of the missing transverse momentum twovector

~P miss

T

R jj

> 0.6 for any pair of jets

(and its magnitude ET

miss ) is then based on the transverse

momenta

Number

of

of jets 7 8 6 7

E miss

T

/ p all electron and muon candidates, all jets

which are not alsoHelectron T candidates > 3.5 with GeV |⌘| 1/2

< 4.5, and all

calorimeter clusters with |⌘| < 4.5 not associated to such objects.

-1 Data 2011 ( s = 7 TeV)

5

∫L dt ~ 1.34 fb

5

Table 1: Definitions of the four signal regions.

10

Total SM Prediction

10

QCD+tt→ qq (Template)

Following the steps above, 4overlaps ATLAS between candidate jets

Alpgen tt→ ql,ll

4

10

10

Alpgen W→ (e,µ,τ)ν

with |⌘| < 2.8 and leptons are 3 resolved as follows. First, any

10

Alpgen Z→ νν

3

SUSY Point (1220,180)

10

SR

such4. jet Event candidate Selection lying within 2

a distance R Multi-Jet < 0.2 Control ofRegion

an elec-

2

10

10

tron is discarded, where R = p > 55 GeV

T

10

( ⌘) 2 + ( ) 26 . jets Then p any lep-

10

ton candidate Following remaining the object within reconstruction described in Section 3,

1

a distance R = 0.4 of such a

1

jet candidate events areis discarded. if any Thereafter, electrons or muons remain, or if

-1 all jet candidates with

-1

10

10

2

they contain any jet failing 0

quality 2 4

selection 6 8 10

criteria 12 14

designed

16

2

|⌘| > 2.8 are discarded, 1.5

1.5

C and the remaining electron, muon and

1

1

to suppress detector noise 0.5 and non-collision backgrounds [21],

0.5

jet candidates are retained as reconstructed objects.

0

or if they lack a reconstructed 0 primary 2 4 6 vertex 8 10 with five or more

miss

1/2

E T

/

12 H T

(GeV

14 )

16

0

1.5associated tracks.

2 3.5 EtMiss/√HT [GeV 1/2 ] (a)

When defining control regions that require the presence of one or more leptons,

additional

Four di↵erent signal regions (SRs) are defined as shown in

Figure

requirements

1: The distribution

are applied.

of the variable

Electrons

E

Table 1. The use of multiple signal miss must pass the ‘tight’ selection

criteria of Ref. [20], and the sum ⌃ of the transverse regionsmomentum providesof sensitivity tracks

within

normalised to the data in the region with E

inadi↵erent cone of R areas = 0.2of around MSUGRA/CMSSM the electron T

miss

must satisfy ⌃/p plane. T (e) < Furthermore,

0.1.

Muons mustthe havecomplementarity longitudinal and transverse

of theimpact selections

parameters

maywithin be enhanced

1 mm

and 0.2 mm of the primary vertex, respectively, and must have ⌃ < 1.8 GeV.

in new models not explicitly considered here. The combina-

E T

Miss

+(≥6-8)jets+0 leptons

selections and backgrounds

multi-jet background estimate

SR background = BxC/A

Thursday, November 10, 11

1/2

Events / 0.25 GeV

DATA / Prediction

1/2

Events / 0.25 GeV

DATA / Prediction

MSUGRA/CMSSM models. Di↵eren

ing and splitting between 1.3 fbthe -1 o✏ine a

lead to trigger ine ciencies. A separ

arXiv:1110.2299

tween all jets with p T above the thresh

accepted by JHEP

to maintain acceptable trigger e cienc

The final selection variable is ET

miss

nitude of the missing transverse mom

of the scalar sum H T of transverse m

p T > 40 GeV and |⌘| < 2.8. This rati

the size of the missing transverse mom

olution due to stochastic variations in t

definition

H T = scalar sum of p T of jets with

p T > 40 GeV and < 2.8

Targeting gluino pair production

and long decay chains

Based on multi-jet triggers

5. Backgrounds, Simulation and No

Multi-jet -1 and Data fully 2011 (


hadronic

L dt ~ 1.34 fb

s = 7 TeV)

ttbar: ET Miss /√HT Total SM Prediction

QCD+tt→ qq (Template)

ATLAS

shape

Alpgen tt→ ql,ll

the signal regions.

Alpgen W→ (e,µ,τ)ν

invariant with jet multiplicity,

Alpgen Z→ νν

SUSY Point (1220,180)

measured with Multi-Jet Control 5-6 Region jets

Standard Model processes contribu

The dominant ba

production, including those from pure

cesses and fully hadronic decays of t¯t;

5 jets p > 80 GeV

T

decays of t¯t; and leptonically-decaying

W, semileptonic top: CR with

one lepton, 40 55 GeV or (b) exactly five jets with p T > 8

Overlaid are templates taken from selections requiring (a) exactly five jets with p T > 55 GeV or (b) exactly four jets with p T > 80 GeV. These templa

/ p H T < 1.5. The background estimation includes the ALPGEN Monte-Carlo prediction for the ‘leptonic’ St

Model backgrounds. For illustrative purposes the plots also contain the distribution expectedfrom for an example the multi-jet MSUGRA/CMSSM processes point with can m 0 be = 1220 det G

m 1/2 = 180 GeV. In all ratio plots (lower), in regions with very low numbers of events, some points may lie o↵ the shown range and for bins with no observed

no ratio is shown. For t¯t backgrounds the labels ‘qq’ and ‘ql,ll’ represent fully hadronic and non-fully-hadronic decays respectively.

11

measurements. In events dominated by


E T

Miss

+(≥6-8)jets+0 leptons

results

Signal region 7j55 8j55 6j80 7j80

Multi-jets 26 ± 5.2 2.3 ± 0.7 19 ± 4 1.3 ± 0.4

t¯t ! q`, `` 10.8 ± 6.7 0 +4.3 6.0 ± 4.6 0 +0.13

W + jets 0.95 ± 0.45 0 +0.13 0.34 ± 0.24 0 +0.13

Z + jets 1.5 +1.8

1.5

0 +0.75 0 +0.75 0 +0.75

Total Standard Model 39 ± 9 2.3 +4.4

0.7

26 ± 6 1.3 +0.9

0.4

Data 45 4 26 3

N 95%

BSM,max

26.0 11.2 16.3 6.0

⇥ ✏/fb 19.4 8.4 12.2 4.5

95%

BSM,max

p SM 0.30 0.36 0.49 0.16

Table 2: Results for each of the four signal regions for 1.34 fb 1 . The expected

550 ATLAS

obs. CL s 95% C.L. limit

number of Standard miss

Multijets plus E Model Combinedevents are exp. CL 95% C.L. limit

given for each of the following sources:

s

T

multi-jet 500 (including fully hadronic exp. t¯t), limit semi- ±1 σ

and miss fully-leptonic top combined,

2011 ≥2,3,4 jets plus E

T

and W and2-4 Z bosons jets limit (separately) in association with jets, as well as the total

450

CL 95% C.L. limit

arXiv:0811.2512.

Standard Model expectation. Where s

±

LEP small 2


χ

1 event counts in control regions have

-1

not 400

D0 g,

~

made it possible to determine a central ~

arXiv:0712.3805.

q, tanβ=3, value µ 520 GeV at 95% C.L.

200

A 0 = 0, µ>0 slice of MSUGRA/CMSSM ~ g (600)

5 . Data from the four

SRs 150 are used to set the limits, taking the SR with the best expected

500 limit 1000 at each 1500 point 2000 in parameter 2500 3000 space. 3500 The limit for each

m

SR is obtained by comparing the observed 0

[GeV]

event count with that

expected from Standard Model background plus SUSY signal

= 10, A 0 = 0,µ > 0 slice

processes, taking into account uncertainties in the expectation

Figure 5: Combined exclusion bounds in the tan

Thursday, of the MSUGRA/CMSSM November 10, 11 space. Gluinos with masses below 520 GeV, and

12


squark-squark and squark-antisquark VII. EVENT SELECTION production is

ATLAS [31] is a particle physics detector 1.04 fb 6

considered. This is achieved by setting all other

-1 ATLAS

with

E

Miss T +jets+1

The kinematic

lepton

selections start by requiring the presence

of exactly one lepton (electron or muon) with p

SUSY forward-backward particle masses, including symmetric thosecylindrical of thirdarXiv:1109.6606

forward-b

gen-geometreration Standard nearsquarks, Model 4π 25 coverage GeV to multi-TeV in case inofsolid an values. electron angle and This [32]. p T Standard > model submitted

an

signal 10

6

6

selection and backgrounds

T >

ATLAS

Data 2011 ( s=7 TeV)

10 ATLAS

Data 2011 ( s=7 TeV)

near

20 The Model GeV inner to PRD

4π c

for

-1

multijets (data estimate)

-1

multijets (data estimate) tor (ID)

detec

5

10 ∫L dt = 1.04 fb

5

W+jets

10 ∫L dt = 1.04 fb

W+jets

is characterized

Z+jets tor (ID) muons. consists by three If another of freea parameters: lepton silicon is reconstructed pixel m˜q Z+jets

, detector, mwith p T > ˜χ

0,

4

Electron Channel tt

20 GeV (“medium”

4

electrons) Muon Channel or p

10

single top

10

T > 10 tt GeV (preselected

−detector mmuons), ˜χ

microstrip a silico

single top

and

Dibosons microstrip x =(m

Looking for 3gluino and squark decays MSUGRA m =500 to m LSP, ˜χ

± 0)/(m˜q the(SCT), −event m ˜χ is

0). rejected and ina order transition =330

Dibosons to minimize

miss

10

0 1/2 3

(EφΔ ,jet )>0.2

T 1,2,3,4

Background estimate:

but with one lepton in decay chains.

10

MSUGRA 4 m 0

=500 m 1/2

tracker radiatio (T

=330

miss

(EφΔ ,jet )>0.2

tracker (TRT). overlap with The otherID analyses is surrounded aimed final states

T 1,2,3,4by awith

thin super

quarks and gluons 2

2

10 of less than 1%.

• In the gluino-chargino-neutralino

anhigher integrated lepton luminosity multiplicities.

10 of 1.04 fb

model, −1 , with an estimated

hereafter conductin

The missing transverse momentum ET

miss in

conducting

this analysis

is the opposite 10 of the vectorial p 10multi-jet from data, using a control

uncertainty Atsolenoid least of 3.7% three [54].

providing or four good jets a 2with T pseudorapidity magnetic field, an

example:

T

called gluino model, the decay chain ˜g → q¯q ˜χ ± by high-gr


sum of reconstructed

objects in the event, comprisedq¯qW of the jets with

by high-granularity |η| < 2.8 are required, liquid-argon depending (LAr) on the selection, sampling as electro

1

outlined below.

1sample Large mismeasurement with looser lepton of the jetselection.

transverse

calorimeters.

p T > 20 GeV, the signal lepton, any additional

T . This magnetic (∗) ˜χ 0

magnetic

is assumed to have a 100% branching

identified

con-

VII. EVENT SELECTION

momenta are avoided Hadron by requiring calorimetry that E isby T

-1

-1

Signal selection:

miss

provide an iron

non-isolated muons, and three-dimensional fraction, calorimeter and only gluino-gluino production is considered.

This is achieved by setting all other

10

10

clusters with |η| < 4.5 not belonging to Tany of can

by the be aforementioned

object types.

an

es-

iron-scintillator The not kinematic aligned with

2

2W(ttbar) any of the

control

three region:

four selected

40 <

jets

MT < 80

T (hole). Projecting this (∆φ(jet i ,

Single electron or muon trigger, 1 electron

⃗ selections start tilebycalorimeter requiring presence

of exactlyE one miss lepton

in the central pidity ran

T ) > (electron 0.2 ). Kinematic or muon)

GeV, 30 < ET Miss withdistributions p T

SUSY

> after

During a part 1 of the data-taking

T gives period, the anpidity quantity electronics

failure in the LAr barrel EM calorimeter

range. 25 1

< 80 GeV, b-tag veto

(hole)

(muon),

= Emiss T with (hole) 0

pT · > cos 25 ∆φ(jet, (20)

EGeV, ⃗ application

GeV case The of anend-cap theelectron leptonand andp and T jet

>

selection

20forward GeV regions

strumente

particle masses, including those of all squarks, requirements to are in

T

miss created a

). Events

muons. If another lepton is reconstructed with p

MT > 100 are shown in Figure 0(one 1b-tag for atjet), least all three other jets T > netic and

dead region in the cuts and Figure same 2as SR.

0

second

100

and third

200

layers,

300 multi-TeV corresponding

to approximately 1.4 × 0.2 in ∆η × ∆φ. Events with T

strumented

400 500values.

600

0 100 200 300 400 500 600

miss

miss

T (hole) > 10 GeV and ∆Emiss T

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ter (MS) i

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10 ATLAS

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ter ± −(MS) m

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0 T · Emiss 50 T

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The effective mass m eff is obtaineda wide from objects variety in theof models the analysis can of be thededuced 2010 data [4]. from At leastlimits three on tion with

event as the scalar sum

simplified models [25]. jets, 2. “Tight” with p T 3-jet > 60 GeV selection for the(3JT). leadingInjet, the andtight 3-jet se- GEN [33], 13

uark-antisquark production is

achieved by setting all other

s, including those of third genulti-TeV

values. This model

ree free parameters: m˜q , m ˜χ

0,

0)/(m˜q − m ˜χ

0).

p T > 20 GeV, the signal lepton, any additional identified

non-isolated muons, and three-dimensional calorimeter

clusters with |η| < 4.5 not belonging to any of the aforementioned

object types.

During a part of the data-taking period, an electronics

failure in the LAr barrel EM calorimeter created a

dead region in the second and third layers, corresponding

to approximately 1.4 × 0.2 in ∆η × ∆φ. Events with

an electron in this region are vetoed, leading to loss of

signal efficiency of about 1%. The energy measurement

for jets in the data in the problematic region is underestimated.

A correction to the jet energy is made using

the energy depositions in the cells neighbouring the dead

region, and this is also propagated to E miss

tribution of jets in the dead region to E miss

timated and is denoted as E miss

quantity on the direction of E miss

Events / 10 GeV

o-neutralino model, hereafter

the decay chain ˜g → q¯q ˜χ ± →

d to have a 100% branching

uino-gluino production is conved

by setting all other SUSY

∆ET

miss

uding those of all squarks, to

his model is also characterrameters:

m˜g , m ˜χ

0,andx =

m ˜χ

0).

Data / SM

Events / 10 GeV

Data / SM

V

with ∆E miss

0.1 are rejected. This requirement rejects less than 0.5%

of the events in the signal regions, and up to 2% of the

events in the control regions.

In the event selection, a number of variables derived

from the reconstructed objects are used. The transverse

mass m T formed by E miss

defined as

e third generation squarks in

ated by the fact that the pheeneration

squarks (production

rks) is covered by a separate

r each choice of the three free

definitions

ed models, the sparticle mass

e, and the sparticle decays are

where p jet i

odels are used to identify the

leading jets.

of the search, characterize a

The effective mass m eff is obtained from objects in the

event as the scalar sum

Thursday, November 10, 11

Data/MC overflow = 0/0.6

Data/MC overflow = 1/2.2

Events / 10 GeV

Data / SM

Events / 10 GeV

Data / SM

nal regions, and to assess sensitivity to specific SUSY

V

Data/MC overflow = 0/0.2

Data/MC overflow = 0/3.9


ing transverse momentum. However,

Fitted top events 47 ± 16 (38) 8.9 ± 3.2 (7.3) 142 ± 14 (115) 70 ± 7(57)

ecaying to the lightest neutralino minimal (LSP) and particle an on-shell content from the for

Fitted W/Z events 16.6 ± 9.4 (20.1) 5.0

used the decay final

± 3.2 (6.1)

to optimize

ofstate a squark under

19.0 ± 4.8 (23.2)

the study. selection.

or a gluino, LSP

322 ± 23 (393)

Onlyi

v

Fitted Emultijet events

Miss T +jets+1

0.0 +0.0

lepton

−0.0

0.0 +0.6

−0.0

5.4 ± 2.2 21.6 ± 5.7

r off-shell W boson: ˜χ ± → W (∗) ˜χ This 0 can be achieved

. The chargino arises following by assuming

istwo considered

that models all SUSY

inconsidered:

this

particles

analysis since

decay

in

Fitted sum of background not of events interest to 64 a± 19 specific model 13.9 ± 4.3 are very 166 ± massive 13 and 413 ± 20 Such d

rom the decay of a squark or a gluino, via one of the of the 14 LSP, the electron channels are h

decouple. In order to • achieve In the a final massstate hierarchy with leptons, corresponding

ollowing two models considered:

results

favor of the µ- andτ-producing

decay

mod

TABLE II: Fit results for the electron (top part) and muon (bottom

the

part)

simplified

channels in the

models

“loose” 3-jet (3JL)

considered

and

squark-chargino-neutralino

“tight” 3-jethere contain a TABLE III: Fit results for the electron (top part) and muon (bottom part) channels in the “loose” 4-jet (4JL) and “tight”

(3JT) signal regions. The results are obtained from 4-jet the (4JT) control signal regions regions. usingThe the results “discovery are obtained fit” (see text fromfor the details). controlregionsusingthe“discoveryfit”(seetextfordetails).

ing Nominal to a long lifetime (cτ

MC • expectations In the (normalised mass to hierarchy MC cross-sections) Nominal corresponding are given MC expectations betweenparenthesesforcomparison.

(normalised to to sequential

> decay, ing tra he

∼ 15 mm)

decaying to the lightest neutralino

MC cross-sections) are the given between parentheses for comparison.

considered squark (LSP) model, and an

here. the on-shell decay chain used t

Electron squark-chargino-neutralino channel 3JL Signal Electron region channel decay, or 3JToff-shell Signal region hereafter W4JLboson: Signal Top called

region region˜χ ± 4JT Signal region Top region W region

q → ′ W (∗) (∗) ˜χ ˜χ 0 . Data is Theassumed consistent chargino with arises to SM haveis acon

1

Observed events Observed 71 events 14 4162 5659 1382 1872

the squark model, the decay from chain the ˜q decay → q ′ of ˜χ ± a →squark or a gluino, expectation via one for all of selections the of the

ing fraction, and only first- and seco

Fitted top events 56 ± Fitted 20 (51) top events 7.6 ± 3.0 (6.8) 38 125 ± 1516 (34) (112) 4.564 ± 2.6 ± 8(58) (4.1) 1258 ± 44 (1138) 391 ± 14 (354)

Fitted W/Z events 35 ± 20 (34) 10.5 ± 6.5 (10.1) 30.1 9.1 (29.3) 425 36 (413)

q ′ W (∗) ˜χ 0 is assumedFittedto W/Z events

have

following

a 100%

two models

9.5 ±

branching

fraction, and only first- and

considered:

7.5 (9.2) 3.5 ± 2.2 (3.4)


1.04 fb -1

troduction

E

Miss T +jets+2 lepton

21 SUSY events can arXiv:1110.6189

produce charge

SUSY events can produce charged leptons with 22 high transverse high momentum submitted (p

selections and backgrounds

T ) through to PLB t

ansverse y extensions momentum to the Standard (p T ) through Model the (SM) decays predict of ofneutrali-

and and charginos. of new states Thethat maindecay processes to invisible producing par-leptons

are: (a) ˜0i ! l± ⌫ ˜⌥

,(b)˜±

23 nos and charginos. The main process

os istence

re: : (a) (a) ˜0i

˜0i ! l± l± ⌫ ˜⌥

,(b)˜±

j j i

! l ± ⌫ ˜0j ,(c)˜0i ! l± l± l ⌥ l ⌥ j i ! l ± 24


New coloured particles, such as the squarks (˜q) and ˜0j ˜0j

(d) ˜±

i ! l ± l ⌥ 25

˜±

j (for i>jan

nd uinos (d) (d) Supersymmetric (˜g)

˜±

˜± of events can have two leptons if (c) or (d) happen in one decay chain (leptons

i i ! supersymmetric l l ± l l ⌥ ˜±

j j

(for (SUSY) i>jand theories i>0), [1], are where

26

lanl is is e, µ or ⌧ lepton (only e and µ a

n have same flavour and opposite sign) or if (a) or (b) occur both chain (leptons might have

e,

those e, µ µ or or predicted.

⌧⌧ lepton These (onlynew e and particles µ are could considered be acle

different flavour and/or same sign).

27

in inthis

paper).

this

aper). at the Large Hadron Collider (LHC). In R-parity

28 In each SUSY event there are two

ving [2] SUSY models, the lightest supersymmetric

Analysis 1: Opposite sign inclusive search 29

nIn each eachSUSY event there are two independent cascade decays. Two leptons are produced in

le (LSP) is stable and weakly interacting, and SUSY cascade

Signal Region 30

ecays. Two Two

Three leptons leptons

signal are are

selections produced in

(see table) in events eventsinin which whichtwo

gauginos OS-SR1 decay OS-SR2 via OS-SR3 cascade SS-SR1a) SS-SR2 or b), FS- o

les are pair-produced. The LSP escapes detection, ET miss [GeV] two 250 220 100 100 80

31

auginos

ginos decay

decay

via

via

cascade

cascade

a)

a)

or

or b),

b),

or

or

events

events

in Leading

in

which jet p

rise to events with significant missing transverse mom

(E decays

T [GeV]

which

one

gaugino

-decays 80

via100 cascade- c) or

50

d)

one

augino

gino miss

Second jet

32

p T [GeV]

the events

-

may

40

contain

70

same

-

sign

50

le

T decays Main ). The background via dominant cascade

via cascade is dileptonic SUSY c) or d). production

c) or d). top In

In pairs. the chantethe

events LHCmay are: contain squark-(anti)squark, same sign leptons squark-gluino andNumber theoflepton

jets - 3 4 - 2

former Third jet p T [GeV] case, - 40 70 - -

the Fourth former jet33

p T [GeV] case, flavour may - di↵er. - In 70 the latter - case, -

events

Analysis

may contain

2: Same sign

same

inclusive

sign leptons

search

and m the lepton

luino avourpair mayproduction. di↵er. In the The latter squarks case, and thegluinos leptons

ll veto [GeV] 34 opposite-sign and - same - flavour, - and - 80 s

are will have

ted

our may di↵er. In the latter case, the leptons will 35 of have same-flavour dilepton events over d

pposite to decay sign and into same quarks flavour, and the and SUSY searching partners Table 1: for Criteria an ofdefining excess each of the three signal for the opposite-sign (OS-SRx) analysis,

osite sign Two and signal same selection flavour, (see table)

same-sign analysis (SS-SRx) 36

fuge same-flavour and Higgsdilepton bosons, charginos, events over

and˜±, di↵erent

searching and neutrali- flavour

for an

events

excess o↵ers and each of one the three of the regionsbest for the flavour-subtraction routes to (FS-SRx) the mo ana

FS-SR3 are identical.

↵ers ame-flavour 0 37

. Weak one ofgauginos dilepton events over di↵erent flavour events surement of SUSY particle masses v

SM the rate best and

very routes sleptons

small, from the dibosons model-independent may also be pairced

rs rement one andofdilepton the SUSY bestsearches routes particleto are masses the potentially model-independent 245

or opposite sign mea-

244 muons dimuon events 38 dilepton for which with the mismeasured |zinvariant 0 | and |d 0 | require- mass

287 charge ground distribution

from charge misid

via end-points very sen-

meaement

ilepton direct Analysis of invariant weak SUSY 3: gaugino Flavour mass particle distribution production: subtraction masses via [3–5]. search ˜±1

the

end-points ˜02,

ments have

˜±1 ˜01,

been relaxed. The region 1 < |z 0 | < 100 mm288

same-sign signal region.

246 is populated with cosmic rays. Due to the fall o↵ of the The fully leptonic t¯t b

39 in the Previous results of SUSY searche

247 tracking e ciency at large z 0 , this region can be well de- is obtained by extrapolati

248 scribed by a Gaussian fit. This fit can be used to evaluate in a suitable control regio

pton and ˜02

invariant ˜02.

mass distribution [3–5].

40 nal states with two leptons, electro

249 the number of cosmic rays in the region |z 0 | < 1 mm, given nation from non-t¯t events

Previous Look results for an of excess SUSY of e ± searches e ∓ +μ ± μ ∓ over at e ± μ ∓ 250 the estimated LHC . Sensitive

number forin to

the fi-regioal (c) or

1 <

(d).

|z 0 |

Main

< 100 mmbackground af- MC ratio.

(top)

The numbers o

trevious submitted

statescancels results with

to Physics

in two the ofLetters leptons, subtraction SUSYB

251 ter the application of the signal region selection cuts. This

searches electrons average. at orprocedure muons, LHC

yields contributions canforbe

fi-

from cosmic rays of < 10 3

252

253

states with two leptons, electrons or muons, can be

Thursday, November 10, 11

Not reviewed, for internal circulation only

254

events in each signal region. The coincidence of a single

reconstructed collision electron and a single reconstructed

October 13, 2011

gion are determined using

top-tagging requirement i

variable m CT [28]. This o

the four-vectors of the sel

15


E T

Miss

+jets+2 lepton

results

Data are in good agreement with

SM expectation for all signal

regions

Thursday, November 10, 11

16


E

Miss T +jets+2 lepton

443

results

truction probabilities themselves. This systemup

most of the total systematic uncertainty on457

assumed to be degenerate and the branching ra

22 fb, m(˜±1 25 fb, ) 429 = m(˜02). fb, 27 fb and The 17masses fb, respectively, for slepton at the 95%

456

SS-SR2 24.9 ± 4.1 ± 4.2 flavo 28

confidence level.

round construction probabilities themselves. This systemakes

up most of the total systematic uncertainty on assumed toThe be ) ± degenerate SS = and m(˜02). ˜02

m(˜±1 ) = m(˜02).

456

mis-reconstruction

yields in SS-SRx.

probabilities themselves. This system-

! ˜l The masses for slepton flavours are

428

m(˜±1 ± ⌫, ˜⌫l

The

! ˜l masses ± l ⌥ 458

decay

for slepton

are set

456

Table 3: Predicted background events, flav the

457

atic makes up most of the total systematic uncertainty

459 8. Summary Also on shown selection and without the branching jets is also ratios for

429

ckground yields in SS-SRx.

˜±1

! ˜l ± assumed are

457

⌫,

sensitive

˜⌫l ± events to thebe degenerate

and ˜02

to electroweak

! ˜l ± l ⌥ and the branching r

458

decay

production

are set to one.

430 the background yields in SS-SRx.

˜±1

! ˜l

and observed the corresponding and expected ± ⌫, ˜⌫l ± and ˜02

! ˜l

95% CL limit upper lim c

egion OS-SR1/FS-SR3 OS-SR2 OS-SR3 460 For ± l ⌥ 458 this production lated using mode, the CL s leptons technique, are decay for each produced are opposi set

459

al 7% 10% 21% Also This shown Letter

Also

reports

cascades:

are the observed and expected limit contours.

459

l Region OS-SR1/FS-SR3 OS-SR2 OS-SR3

of ˜±1

shown ˜02 signal a search

, if are

region.

they for

! (⌫˜l ± decay observed

new

)(l ±˜l⌥ physics

to slepton: and expected

in

) ! (⌫l ± final states ˜01)(l limit ± l ⌥

461

Signal Region OS-SR1/FS-SR3 OS-SR2 460OS-SR3

containing

11% 6% 6%

For this production mode, leptons are produced in the

460

˜±1

stical Statistical 7% 7% 10% 21% 10% cascades: ˜02 high-p

For this T

!

˜±1 ˜02 (l ±˜⌫)(l jets,

production

missing

! (⌫˜l ±˜l⌥ transverse ± )

)(l ±˜l⌥ ! mode, (l

) ! ± leptons

momentum

⌫ ˜01)(l

(⌫l ± ˜01)(l ± lare ⌥ produce

and no

462

± l ⌥ 461electrons 21% or muons ˜01)

(wit

and

JES 11% 11% 6% 6% ˜±1 ˜02 ! (l ±˜⌫)(l 447

cascades: with The p

˜±1 ˜02 ! (⌫˜l ±˜l⌥ ) ! (l ± ⌫ ˜01)(l ± )(l ±˜l⌥ ) ! (⌫l ± l ⌥ 462 6%

˜01) ± ˜01)(l ± l ⌥

461

1% 11% 15%

T signal > 20 region GeV. Data SS-SR1 recorded is particula by the

463

ATLAS branching experiment ratios).

˜±1 ! (l ±˜⌫)(l The cross section for ±˜l⌥ ) ! (l ± ⌫ ˜01)(l (with

the ± l ⌥ 462

˜01) equal

poi

(wi

r

JER

16% 1% 1%

13% 11% 15% 11%

58%

463 15% branching m(˜±1 )=m(˜02) 448 amass the LHC, weakcorresponding gaugino production to an integrated and th

464

luminosity ratios). The cross section for the point with

rator Generator16% 16% 13% 58% 13% m(˜±1 )=m(˜02) 463

ofbranching 1.04 449 fbparticle −1

ratios).

= have 200 cascades been The

GeV used. cross into is Good 0.51

section leptons. pb agreement for

[20]. Inthe Fig. Mis

po

20% 16% 26%

464465

seen 58% the between low-mass m(˜±1 )=m(˜02) 464 the(with region section = 200 have GeV limits = 200 is acceptances on 0.51 GeV ˜±1

pb ˜02

450 numbers one of lepton eventsundetected observedis in [20]. 0.51 pair the or of out

pb ⇠5-15% five Models productio [20].

of signal inM

f

FSR ISR/FSR27% 20% 20% 25% 16% 26% 16% 68%

±

465 466 regions 26% the low-mass 465

1

and the thedi↵erences numbers 451 region acceptance)

low-mass fiedhave of direct region events from acceptances weak have expected 50 to acceptances gaugino of 200 from ⇠5-15% GeV, production SMoffor sources. ⇠5-15% andLSP-

e m

l 27% 25% 68%

±

Total 27% 25% 68%

±

1 mass di↵erences Plot: cross from section 50 tolimit 200 as GeV, a function and e ciencies of

466 467 The of exclusion ⇠20%. 466

467 of ⇠20%. If 1limits 452 If mass slepton Ref. placed di↵erences [33], modes non-SM are from illustrated are 50 cross dominant, to 200 sections GeV, chargin and e

ummary of the dominant systematic mis-reconstruction uncertainties probabilities on the

of the slepton ⇠20%. mass If modes of slepton and aremodes dominant, are dominant, charginoschargi

with

428

467

468

themselves.

f: Athe summary fully-leptonic Table of 2: the A summary dominant t¯t event ofsystematic the yields dominant uncertainties each systematic opposite-sign uncertainties on the

masses up This 200system-

GeV are excluded, m(˜±1 ) = under m(˜02).

as a impose functio

new constraints 453 scenarios LSP (˜01)

with 456masses.

novel physics. The results thein The assu Fi

on the

429

468 masses468

up to masses 200 GeV up toare 200excluded, GeV are excluded, under theunder assumptions the n. es of The thestimates uncertainties fully-leptonic of the t¯t are

fully-leptonic event

atic

di↵erent yields

makes t¯t

in inevent up

each most yields opposite-sign

of

signal

in

region,

each the total opposite-sign

The systematic of

results

these simplified

are uncertainty 454interpreted ton masses models. onin 457both between assumed a simplified theto LSP bemodel and degenerat neutr containing

only squarks

egion. The signal uncertainties region. Theare uncertainties the di↵erent background inareach di↵erent signal yields inregion,

each SS-SRx. signalof region, these simplified of these simplified

Limits assuming

models. models.

430

h has a di↵erent control region.

100% ˜±1

! BR ˜l 455 of the first in ± ⌫, sleptons ˜⌫l ± 458 two generations, a gluino andoctet

˜02

each has because a di↵erent each has control a di↵erent region. control region. and a massless

are

neutralino,

∼±

∼also 0 ~ shown. ~ as

∼~

well 459

∼Also as in

0 ∼0shown MSUGRA/CMSSM

are the observ

int

-1

ed, for internal circulation only

Thursday, November 10, 11

ly

and gluinos are assumed to be mass-degenerate. These limits

442 kinematic cuts at particle level) and e c

remain essentially unchanged if the ˜χ 0 1 mass is raised as high

reconstruction and identification e cien

as 200 GeV. In the case of a specific SUSY-breaking scenario,

444 using the CL s prescription, as described

i.e. CMSSM/MSUGRA with tan β = 10, A

445 resulting limits in each 0 = 0, µ>0, the

signal region for

limit on m 1/2 reaches 460 GeV for low values of m

446 and same-sign analyses are given 0 ,andequal

in Tab

mass squarks and gluinos are excluded below 950 GeV. The use

of signal selections sensitive to larger jet Background

multiplicities thanin Ob

[5] has improved the ATLAS reach at large m

OS-SR1 15.5 ± 0 . The five signal

regions Model are usedindependent to set limits on limits σ on

1.2 ± 3.8 13

OS-SR2 new = σAɛ, fornon-SM

13.0 ± 1.8 ± 3.6 17

cross-sections (σ)forwhichATLAShasanacceptanceA and a

OS-SR3 5.7 ± 1.1 ± 3.4 2

detection efficiency of ɛ [44]. The excluded values of σ new are

SS-SR1 32.6 ± 4.4 ± 6.0 25

[GeV]

± 0 ~ ~ ~ 0 0

χ


χ


ν

0

χ


χ

int 0 0

χ→χ

lν→

± ~ ~ ~

ll, χ


llν

ll χ

∼ll, →l

νlν

lν ll →ll, ll lν

∼lν

ll χ→ ll lν

-1



= ll 1.04 χ

∼L

fb= int

-1

L 1.04

, = s=7 1.04 fbTeV

fb,

1 2

,

1 2

1 2 460 1 1

1 1

1

5

350 m ± = 0, ~ = LSP

+ 1/2 (m - m

χ ∼ 350 ±

0

350 m ±

0)

χ ∼

= m 0, = m 0, ~ = m + 1/2

± χ ∼

(m - m )

4

l, ν

χ ∼ m ~ χ ∼ = m LSP

χ ∼

± χ ∼

l, ν

∼ + 1/2 (m -

χ ∼ m 0)

χ ∼

χ ∼

461

±

1

LSP

2

χ ∼

l, ν


χ ∼

1

1 1 2 2

1

1

1

1

1

CLs observed CLs limit observed 462 limit

3

Signal Region OS-SR1/FS-SR3 models with OS-SR2 tan β = OS-SR3 10, A 0 = 0andµ For this> production 0. In the simplified

model, 10% gluino and 21% squark masses cascades: below˜±1 700 ˜02 ! (⌫˜l ± )

mod s=

Statistical 7%

JES 11% 6% 6% ˜±1 ˜02 ! (l ±˜⌫)(l GeV and

875 GeV respectively are excluded at the 95% confidence ±˜l⌥ level ) !

[GeV]

0

1

0

1

[GeV]

0

1

χ ∼

the mass hierarchy, m˜l

= m ˜0

1

+ 1 2 (m

s=7

CL [pb]

17


modelling is taken modelling from HERWIG is taken without frommodification.

HERWIG without modification. gia; BMB

In the limit of light In neutralinos, the limit of light withneutralinos, the assumption withthat the 0.83 the assumption fb -1 GSRT, that Gr

coloured sparticles coloured are directly sparticles produced are directly and decay produced directly and todecay ter, directly Israel;

jets and ˜χ 0 1,thelimitsonthegluinoandsquarkmassesareapproximately

700 proximately GeV and 875700 GeV GeV respectively and 875 GeV for squark respectively or for Poland; squark G

jets ˜χ 0 ATL-CONF-2011-098

rocco; FO

gluino masses below 2 TeV, rising to 1075 GeV ifmania; the squa M

and gluinos are assumed to be mass-degenerate. JINR; These lim MS

remain essentially unchanged if the ˜χ 0 Slovenia;

1 mass is raised as h

as 200 GeV. In the case of a specific SUSY-breaking Wallenber scenar

i.e. CMSSM/MSUGRA with tan β = 10, A Bern and

0 = 0, µ>0,

limit on m STFC, the

1/2 reaches 460 GeV for low values of m 0 ,andeq

mass squarks and gluinos are excluded below 950 GeV. dom; The DOE u

of signal selections sensitive to larger jet multiplicities Thethan

cru

[5] has improved the ATLAS reach at large m 0 . The acknowle five s

nal regions are used to set limits on σ new = σAɛ, ATLAS fornon-S T

cross-sections (σ)forwhichATLAShasanacceptanceA mark, No an

detection efficiency of ɛ [44]. The excluded values(Germany

of σ new

22 fb, 25 fb, 429 fb, 27 fb and 17 fb, respectively, (Spain), at the 95 A

the Tier-2

E T

Miss

+b-jets+0 lepton

selections and backgrounds

ring ale

inputs

and gluinos are assumed to be mass-degenerate. These limits

Signal Region ≥ 2-jet gluino ≥ 3-jet masses≥below 4-jet 2 TeV, High risingmass

to 1075 GeV if the squarks

lorime-Targetiny above Leading jet p T > 130 as > 200 130 GeV. In> the 130 case of a specific > 130SUSY-breaking scenario,

ET miss

gluino pair production

> 130

followed remain

> 130

essentially by either

> 130

unchanged g ~ → ~ bb → if

>

the bb

130˜χ 0 1 mass or ~ g is → raised bb as high

In many models, the third squark i.e. generation CMSSM/MSUGRA is the lightest with tanand β = these 10, A 0 decay = 0, µ>0, modes the

erformeach

as might Third have jet branching p T

Second jet p T > 40

limit

> 40

on m 1/2 reaches

> 40460 GeV for

> 80

low values of m 0 ,andequal

ratios – close mass > to 40 squarks 100% and > gluinos 40 are excluded > 80 below 950 GeV. The use

rrected

of signal selections sensitive to larger jet multiplicities thanin

Cuts: Fourth

ET Miss > 130 jet p

nhomors

based ∆φ(jet, ⃗P miss

T

GeV, T leading – jet [5] pT has

– > 130 improved GeV, >

the

40 >= ATLAS 3 jets with reach

> 80pT at large > 50 mGeV, 0 . Theno

five signal

regions > 0.25 are used to set limits on σ new = σAɛ, fornon-SM

lepton, ∆ (ET Miss ,jets) > 0.4, ET Miss /Meff ) min > 0.4 > 0.4 > 0.4 > 0.4

cross-sections (σ)forwhichATLAShasanacceptanceA and a

st-beam

Number

E

of T miss

b-jets

/m eff

and meff cut

> 0.3

define detection

>

4

0.25

signal efficiency regions

> 0.25

of ɛ [44]. The

> 0.2

excluded values of σ new are

structed m eff > 1000 22 > 1000 fb, 25 fb, > 429 500/1000 fb, 27 fb and> 17 1100 fb, respectively, at the 95%

primaryDominant background is ttbar for all confidence SR; normalized level. confidence with data level. in a CR with one

rack p 2 lepton and 40 < MT(lep,ET Miss ) < 80 GeV; TF from MC

T , Table 1: Criteria for admission to each of the five overlapping signalregions

r. Only (m eff , E miss and p

T T in GeV). All variables 8. Summary are

Sig. Reg. Data (0.83 fb −1 defined in 8. Section Summary 4. The m eff is

) Top W/Z QCD Total

20 GeV

defined with a variable number of jets, appropriate to each signal region. In the

3JA (1 btag high mass eff >500 selection, GeV) all jets with p361This Letter221 reports +82 a search

−68

121 ± for 61 new15 physics ± 7 in 356 final +103

T > 40 GeV are used to compute the m eff

states

temporeated

a jet.

electrons or muons

−92

3JB (1 btag valuem used eff >700 in theGeV) final cut. The ∆φ63 cut containing is only applied high-p 37 +15 T up jets, to the missing

−12

31 third ± 19transverse leading 1.9 ± momentum 0.9 70 +24 and no

−22

3JC (2 btag m eff >500 GeV) 76 55 +25 with p

−22

20 T > 20 GeV. Data recorded

± 12 3.6 ± 1.8 79 +28 by the

ATLAS experiment −25

approxofthe

3JD (2 btag m eff >700 GeV) 12 7.8 +3.5 a the LHC, corresponding to an integrated

luminosity of 1.04 luminosity −2.9 fb −1 have 5 of ± been 41.04 used. fb0.5 −1 ± Good 0.3 agreement 13.0 +5.6

−5.2is

Signal region

at least

definition

one jet in their decays, seen between for instance the numbers through of events ˜q observed → in the five signal

Table tionef- 2: Summary q ˜χ 0 1,whilegluinostypicallygenerateatleasttwo,forinstance

observed and expected regions event andyields the numbers in the of four eventssignal expected regions. from SM The sources. QCD

prediction . If any is based on the jet smearing method The exclusion described limits placed in theon text. non-SM Systematic cross sections uncertainties impose

through ˜g → q q ˜χ 0 Effective mass distributions in top control region

for ejected,

1.Processescontributingto˜q˜q, ˜q˜g and ˜g˜g final

states therefore lead to events

the Standard Model predictions are given.

new constraints new scenarios constraints withonovel scenarios physics. with novel physics.

an 15%

Thecontaining results are interpreted at least two, in both three a simplified model con-

Thursday, November 10, 11

Referenc

This Letter reports a search for new physics in final sta

containing high-p T jets, missing transverse momentum [1] L.R. andE

electrons or muons with p T > 20 GeV. Data recordedJINST

by

[2] Yu.A.

ATLAS experiment a the LHC, corresponding to an integra

group

have been used. Good agreemen JETP

seen between the numbers of events observed in the five A. sig Nev

regions and the numbers of events expected from SM sourc Nucl.

A. Nev

The exclusion limits placed on non-SM cross sections impo

Phys.

P. Ram

Phys.

The results are interpreted in both a simplified model co

18


Effective mass, 1 bjet selection

E T

Miss

+b-jets+0 lepton

Sig. Reg. Data (0.83 fb −1 ) Top W/Z QCD Total

3JA (1 btag m eff >500 GeV) 361 221 +82

−68

121 ± 61 15 ± 7 356 +103

−92

3JB (1 btag m

results

eff >700 GeV) 63 37 +15

−12

31 ± 19 1.9 ± 0.9 70 +24

−22

3JC (2 btag m eff >500 GeV) 76 55 +25

−22

20 ± 12 3.6 ± 1.8 79 +28

−25

3JD (2 btag SUSY m eff >700 particles GeV) on their 12 decay chains. 7.8 +3.5

−2.9

In5 regions ± 4 0.5 of± parameter 0.3 13.0 +5.6

space with small mass splittings between states, the modelling

Table 2: Summary observed and expected event yields in the four signal regions. The Q

of initial state radiation can affect the signal significance. This

prediction is based on the jet smearing method described in the text. Systematic uncertai

for the Standard modelling Model predictions is takenare from given. HERWIG without modification.

Sig. Reg. Data (0.83 fb −1 ) Top W/Z QCD Total

In the limit

3JA (1 btag m eff >500 GeV) 361 221 +82 of light neutralinos, with the assumption

−68

121 ± 61 15 ± 7 356 +103 that the

coloured

3JB (1 btag m eff >700 GeV) 63 37 +15 sparticles are directly produced and decay directly to

3JC (2 btag m eff >500 GeV) 76 55 +25

3JD (2 btag m eff >700 GeV) 12 7.8 +3.5

translated into 95% C.L. upper limits on contributions from new physics.

−92

Limits are der

using the CL s jets [41] and method, ˜χ −12 0 while31 ± power 19 constrained 1.9 ± 0.9 (PCL) 70

1,thelimitsonthegluinoandsquarkmassesareapproximately

+24

−22[42] method is used

comparison with previous ATLAS results. Upper limits at 95% C.L. on the number of si

−22 70020 GeV ± 12 and 875 3.6 GeV ± 1.8respectively 79 +28

−25 for squark or

events are converted into model-independent 95% C.L. upper limits on the effective cross

gluino masses

tions for new processes. −2.9 below 5 ± 24 TeV, 0.5 rising ± 0.3 to 1075 13.0 GeV +5.6

The results in Table 3 show that the region −5.2if the squarks

3JD provides the

stringent effective andcross gluinos section areupper assumed limit of to17be fb. mass-degenerate. These limits

Table 2: Summary observed and expected event remain yields essentially in the unchanged four signal if regions. the ˜χ 0 1 mass The is raised QCDas high

prediction is based on the jet smearing methodas described 200 Sig. GeV. Reg. In inthe case text.

95% ofSystematic aC.L. specific N events SUSY-breaking uncertainties

95% C.L. σ ef f (pb) scenario,

CL s (PCL) CL s (PCL)

for the Standard Model predictions are given. i.e. CMSSM/MSUGRA with tan β = 10, A 0 = 0, µ>0, the

3JA limit (1 btag on m 1/2 eff >500 reaches GeV) 460 GeV 240 for (206) low values 0.288 of (0.247) m 0 ,andequal

3JB mass (1 btag squarks m eff >700 andGeV) gluinos are 51 excluded (40) below0.061 950(0.048)

GeV. The use

translated into 95% C.L. upper limits on contributions 3JC of (2 signal btag mselections from eff >500new GeV) sensitive physics. 65 to(53) larger Limits jet are multiplicities 0.078 derived (0.064) thanin

using the CL 3JD (2 btag m eff >700 GeV) 14 (11) 0.017 (0.014)

s [41] method, while the power constrained [5] has improved limit the (PCL) ATLAS [42] reach method at large is mused 0 . The forfive signal

regions limits are at 95% used C.L. to seton limits theon number σ new = of σAɛ, signal fornon-SM

comparison with previous ATLAS results. Upper

events are converted into model-independent 95% C.L. upper limits on the effective cross sections

for new processes. The results in Table 3 show that the region 3JD provides the most

22 fb, 25 fb, 429 fb, 27 fb and 17 fb, respectively, at the 95%

stringent effective cross section upper limit of 17

confidence

fb.

level.

Thursday, November 10, 11

Limits on new physics rate and

Table 3: 95% C.L. upper limits on the non-SM contributions to the four signal regions.

correspondingcross-sections PCL limits are given

(σ)forwhichATLAShasanacceptanceA

in parenthesis. Limits are given on the number

andof a

si

events and indetection terms of effective efficiency crossof sections. ɛ [44]. The The systematic excluded uncertainties values of on σ new theare

SM b

ground estimation discussed in Section 5 are included.

The results are also interpreted in terms of 95% C.L. exclusion limits for several SUSY

narios. In Figure 4 the observed and expected exclusion regions are shown in the (m ˜g ) p ,m˜b 1

Sig. Reg. 95% C.L. N events 95% C.L. σ ef f (pb)

for the hypothesis 8. Summary that the lightest squark ˜b 1 is produced via gluino-mediated or direct

production and

CLdecays exclusively via ˜b 1 → b ˜χ

1 0 . The NLO cross sections are calculated u

s (PCL) CL s (PCL)

PROSPINO. For each scenario, the signal region resulting in the best expected exclusion

This Letter reports a search for new physics in final˜

states 19

−5.2


E T

Miss

+b-jets+0 lepton

interpretation

icles on their decay chains. In regions of parameter

small articles mass on their splittings decaybetween chains. states, In regions the modelling of parameter

ate ith radiation small mass cansplittings affect thebetween signal significance. states, the modelling This

ls state takenradiation from HERWIG can affect without themodification.

signal significance. This

ng it is oftaken light neutralinos, from HERWIGwith without the assumption modification. that the

articles limit ofare light directly neutralinos, produced withand thedecay assumption directly that to the

,thelimitsonthegluinoandsquarkmassesareapy˜χ

700 0 1,thelimitsonthegluinoandsquarkmassesareap-

GeV 875 GeV respectively for squark or

d sparticles are directly produced decay directly to

ses telybelow 700 GeV 2 TeV, andrising 875 GeV to 1075 respectively GeV if the forsquarks

or

s asses are assumed below 2to TeV, be mass-degenerate. rising to 1075 GeVThese if thelimits

squarks

inos ntially areunchanged assumed toif be themass-degenerate. ˜χ 0 1 is raisedThese as high limits

essentially . In the case unchanged of a specific the SUSY-breaking ˜χ 0 1 mass is raised scenario, as high

M/MSUGRA eV. In the case with of tan a specific β = 10, SUSY-breaking A 0 = 0, µ>0, scenario, the

/2 SSM/MSUGRA reaches 460 GeV with fortan lowβ values = 10, of A 0 m= 0 ,andequal 0, µ>0, the

ks mand 1/2 reaches gluinos460 are excluded GeV for below values 950 GeV. of m 0 The ,andequal use

uarks lections andsensitive gluinos are to larger excluded jet multiplicities below 950 GeV. thanin The use

lroved selections the ATLAS sensitive reach to larger at large jet multiplicities 0 . The five sigare

used to theset ATLAS limits on reach σ new at = large σAɛ, m 0 fornon-SM . The five sig-

thanin

improved

ons (σ)forwhichATLAShasanacceptanceA are used to set limits on σ new = σAɛ, fornon-SM and a

fficiency ctions (σ)forwhichATLAShasanacceptanceA of ɛ [44]. The excluded values of σ new are and a

Limits on gluino and sbottom masses,

assuming m( ) = 60 GeV and BR(g ~ → ~ b

b) = BR(b

~

→ b ) = 100%

Thursday, November 10, 11

m(g)

~

> 720 GeV for m(b)

~

< 600 GeV

MPO CR and VSC SUSYCR, particles Czechon Republic; their decayDNRF, chains. DNSRC In regions of par

andMPO Lundbeck CR and Foundation, space VSCwith CR, small Denmark; Czech massRepublic; splittings ARTEMIS, DNRF, between European DNSRC states, the mo

Union; and IN2P3-CNRS, Lundbeck SUSYof particles Foundation, initial CEA-DSM/IRFU, state on their radiation Denmark; decaycan France;

chains. ARTEMIS, affect GNAS,

Inthe regions signal European Georgia;

Union; BMBF,

ofsignificanc

parameter

space IN2P3-CNRS, DFG,

with modelling HGF,

small

MPG CEA-DSM/IRFU, is mass taken and

splittings

AvH fromFoundation, HERWIG between France; without states, GNAS, Germany; modification. the Georgia;

Greece; BMBF, of initial DFG, ISF, In state

modelling

GSRT, MINERVA, the HGF, radiation limit MPG ofGIF, light and can AvH affect

DIP neutralinos, and Foundation, the

Benoziyo

signal withsignificance. Germany; the Center,

GSRT, Israel;

assumption Thist

modelling

INFN, Greece; coloured Italy; ISF, is taken

MEXT MINERVA, sparticles from

and

HERWIG

JSPS, are GIF, directly DIP Japan;

without and produced CNRST, Benoziyo modification. and Moroccoter,

FOM Israel; In

Cen-

decay dire

and INFN, the jets NWO,

limit and Italy; of

Netherlands; ˜χ 0 1,thelimitsonthegluinoandsquarkmasses

light MEXT neutralinos, RCN, JSPS, Norway;

with Japan; CNRST, assumption

MNiSW, Mo-tharocco; GRICES

the

Poland;

coloured FOM and proximately and

sparticles NWO, FCT, Netherlands; Portugal; 700 are directly GeVMERYS and RCN, produced 875(MECTS), Norway; GeVand respectively decay MNiSW, Romania;

Poland; MESGRICES of Russia and and FCT, ROSATOM, Portugal; MERYS Russian (MECTS), Federation; Ro-

directly for squ to

jets and gluino ˜χ 0

JINR; mania; MSTD, MESLimits Serbia;

1,thelimitsonthegluinoandsquarkmassesareapproximately

and gluinos 700 GeV are and assumed 875 GeV to berespectively mass-degenerate. neutralino

masses below 2 TeV, rising to 1075 GeV if s

of Russia as MSSR, a and function Slovakia; ROSATOM, of ARRS gluino Russian and Federation; MVZT,

for squark These or

Slovenia; JINR; DST/NRF, MSTD, masses, remain Serbia; South

essentially for MSSR, Africa;

three Slovakia; unchanged

MICINN,

body ~ g → ARRS Spain; ~

b bSRC and MVZT, and

gluino below 2 TeV, rising toif 1075 the GeV ˜χ 0 1 mass if the is raised squarksa

Wallenberg Slovenia; Foundation, DST/NRF, South Sweden; Africa; SER, MICINN, SNSF andSpain; Cantons SRCof

and

and gluinos as 200are GeV. assumed In the to case beof mass-degenerate. a specific SUSY-breaking These limits sc

Bern Wallenberg and Geneva, Foundation, Switzerland; Sweden; NSC, SER, Taiwan; SNSF TAEK, and Turkey; Cantons of

STFC, the

remain

Royal

m(g) i.e.

Society

essentially

~ CMSSM/MSUGRA > 660 Leverhulme

GeV for with

~

unchanged if

Trust,

m( the tan ˜χ 0 ) β

United

< = 200 10,

Kingdom;

STFC, DOE

GeV A 0 = 0, µ>

1 mass is raised as high

Bern and Geneva, limit on Switzerland; m 1/2 reaches NSC, 460Taiwan; GeV forTAEK, low values Turkey; of m 0 ,and

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The jet multiplicities is

limit on m

acknowledged The crucial gratefully, [5] computing 1/2 reaches 460 GeV for low values of m

has improved support particular the from ATLAS fromall CERN reach WLCGat and partners large the 0 ,andequa

m 0

is

mass squarks and gluinos are excluded below 950 GeV. . The Theuse

fi

ATLAS acknowledged Tier-1 facilities nal gratefully, regions TRIUMF are inused particular to(Canada), set limits fromNDGF on CERN σ (Denmark,

ATLAS Norway, Tier-1 cross-sections Sweden), facilitiesCC-IN2P3 at (σ)forwhichATLAShasanacceptanceA

TRIUMF (France), (Canada), KIT/GridKA NDGF (Den-

new

and = σAɛ, the

of signal selections sensitive larger jet multiplicities thanin forn

[5] has improved the reach at large m

(Germany), mark, Norway, INFN-CNAF detection Sweden), efficiency (Italy), CC-IN2P3 NL-T1 of ɛ [44]. (France), (Netherlands), The excluded KIT/GridKA

0 . The five signal

regions are used to set limits on σ values of σ

PIC

(Spain), ASGC (Taiwan), RAL (UK) and BNL new = σAɛ, fornon-SM 20

(USA) and in


the simplified models consideredofhere initial MPO contain stateCR radiation aand chargino VSC can affect CR, Czech the ingsignal transverse Republic; significance. momentu DNRF, This DN

decaying to the lightest neutralino modelling (LSP) andisLundbeck taken anfrom on-shell Foundation, HERWIG without used Denmark; to modification. optimize ARTEMIS, the Eur sel

or off-shell W boson: ˜χ ± → W (∗) ˜χ In 0 1.03 fb

. the Union; The limit chargino of IN2P3-CNRS, light neutralinos, arisesCEA-DSM/IRFU, with considered the assumption France; in -1

this that GNAS, ana the

from

E

the decay Miss of

T +b-jets+1

a squark or coloured a gluino, gia; sparticles BMBF, via

lepton

one DFG, areof directly HGF, the MPG produced ATL-CONF-2011-130

of theand AvH LSP, decay Foundation, thedirectly electron Ger to c

following two models considered:

andGSRT, ˜χ 0 1,thelimitsonthegluinoandsquarkmassesareapproximately

ter, Israel; 700 GeV INFN, and Italy; 875MEXT GeVing respectively and to JSPS, a longJapan; for lifetime squark CNRST or (c

Greece; ISF, MINERVA, favorGIF, of DIP µ- andτ-pr Benoziyo

• In the mass hierarchy corresponding gluino rocco; massesFOM to below sequential and 2 TeV, NWO, rising Netherlands; considered to 1075 GeV RCN, here. if Norway; the squarks MN

squark-chargino-neutralino anddecay, gluinos Poland; hereafter areGRICES assumed called and to be FCT, mass-degenerate. Portugal; MERYS These (MECTS limits

Targeting gluino pair the production squark model, followed the by decay either remainchain ~ g mania; essentially → ~ tt ˜q MES →t unchanged q b of ′ ˜χ Russia ±

or →g ~

if → and the tt ROSATOM, ˜χ 0 1 mass is raised Russian as Feder high

q ′ W (∗) ˜χ 0 is assumed toashave 200JINR; GeV. a 100% InMSTD, the case branching

→ fraction, tt has and larger only acceptance first- i.e. and CMSSM/MSUGRA Slovenia; = second-generation

limits DST/NRF, will be with conservative.

South tan β Africa; = 10, MICINN, A 0 = 0, µ>0, Spain; the SR

Serbia; of a specific MSSR, SUSY-breaking Slovakia; ARRS scenario, and M

III. THE A

If allowed, g → tt

limit onWallenberg m 1/2 reaches Foundation, 460 GeV for Sweden; low values SER, of SNSF m 0 ,andequal

Canto

squark-squark and squark-antisquark production is

Cuts: One electron or muon with pT > 25/20 GeV, mass squarks ET

Bern Miss and and > Geneva, 80 gluinos GeV, are Switzerland; >= excluded 4 jets ATLAS below NSC, with 950 pT

Taiwan; [31] > GeV. 50 TAEK, is Thea use pa Tu

considered. This is achieved by setting all other

GeV, meff > 600 GeV

of signal STFC, selections the Royal sensitive Society to larger and forward-backward Leverhulme jet multiplicities Trust, thanin United symm

SUSY particle masses, including

[5] hasdom; those

improved DOE

of third

the andATLAS NSF,

generation

squarks, to multi-TeV values.

United reachnear States large 4π of America. mcoverage 0 . The five insig-

nalCR regions but The are 40 crucial

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CR for dominant top pair background: same as

This

used < MT(lep,ET tocomputing model

set limits Miss support on tor ) < σ new 100 (ID) from = GeV. σAɛ, consists all WLCG fornon-SM ofpartn

a

is characterized by three free parameters:

cross-sections acknowledged (σ)forwhichATLAShasanacceptanceA

m˜q gratefully, , m ˜χ

0, inmicrostrip particular from detector CERN and (SC an

and x =(m ˜χ

± − m ˜χ

0)/(m˜q detection − m

Results:

ATLAS ˜χ

0). efficiency Tier-1 of facilities ɛ [44]. The at tracker TRIUMF excluded(TRT). values (Canada), of The σNDGF

new are ID

22

54.9

fb, 25 mark,

±

fb,

13.6

429 Norway,

events

fb, 27Sweden), fb

expected

and 17CC-IN2P3 fb, respectively, (France),

signal region

at theKIT/Gr

95%

• In the gluino-chargino-neutralino

confidence (Germany),

model, hereafter conducting solenoid pro

level. INFN-CNAF (Italy), NL-T1 (Netherlands)

called gluino model, the decay (Spain), chain ˜g ASGC → q¯q ˜χ

(Taiwan), ± by high-granularity liqui

→ RAL (UK) and BNL (USA) a

74 events observed

q¯qW (∗) ˜χ 0

magnetic calorimeters.

is assumed to have the a 100% Tier-2 facilities branching worldwide.

8. Summary

by an iron-scintillator ti

fraction, and only gluino-gluino production is considered.

This is achieved by setting all other SUSY

pidity range. The end-

new physics in with finalLAr states ca

This Letter reports a search forstrumented

particle masses, includingcontaining those of

References

high-p

all squarks,

T jets, missing

to

transverse netic and momentum hadronicand meas no

multi-TeV values. This electrons model isor also muons characterized

by three free parameters: ATLASm˜g [1] experiment , m

with p T > 20ter GeV. (MS) Dataisrecorded based on by the thr

L.R. Evans ˜χ

0,andx a(ed.) theand LHC, =

P. Bryant corresponding arranged (ed.), LHC Machine, with to an integrated an eight

(m luminosity JINST of 1.04 3 (2008) fb −1

˜χ

± − m ˜χ

0)/(m˜g − m ˜χ

0).

S08001. have beenaround used. Good

the calorimeters

agreement is

seen between

[2] Yu.A.

theGolfand numbers

and E.P.

of events

Likhtman,

observed

Extensionin of the

five

algebra

signal

of Po

The group generators and violation of P invariance,

have

assumption

been used. Good

of massive

agreement

third

regions is

generation

andJETP the numbers

squarks

Lett. 13 (1971)

ofin

of chambers for the trigg

events

323-326.

expected from SM sources.

the squark model is motivated by Thethe exclusion fact that

A. Neveu limitsthe andplaced phenomenology

of light third generation new constraints squarks Nucl. (production

on Phys. scenarios B31 (1971) with 86-112. novel physics.

surements.

J.H. Schwartz, on non-SM Factorizable crossdual sections model of impose pions,

of top and/or bottom quarks) is coveredA. by Neveu a and separate J.H. Schwartz, Quark model of dual pions, 21

SUSY particles on their decay chains. In regions of parameter

space with small mass splittings between states, the modelling

of initial state radiation can affect the signal significance. This

modelling is taken from HERWIG without modification.

In the limit of light neutralinos, with the assumption that the

coloured sparticles are directly produced and decay directly to

jets and ˜χ 0 1,thelimitsonthegluinoandsquarkmassesareapproximately

700 GeV and 875 GeV respectively for squark or

gluino masses below 2 TeV, rising to 1075 GeV if the squarks

and gluinos are assumed to be mass-degenerate. These limits

remain essentially unchanged if the ˜χ 0 1 mass is raised as high

as 200 GeV. In the case of a specific SUSY-breaking scenario,

i.e. CMSSM/MSUGRA with tan β = 10, A 0 = 0, µ>0, the

limit on m 1/2 reaches 460 GeV for low values of m 0 ,andequal

mass squarks and gluinos are excluded below 950 GeV. The use

of signal selections sensitive to larger jet multiplicities thanin

[5] has improved the ATLAS reach at large m 0 . The five signal

regions are used to set limits on σ new = σAɛ, fornon-SM

cross-sections (σ)forwhichATLAShasanacceptanceA and a

detection efficiency of ɛ [44]. The excluded values of σ new are

22 fb, 25 fb, 429 fb, 27 fb and 17 fb, respectively, at the 95%

confidence level.

8. Summary

This Letter reports a search for new physics in final states

containing high-p T jets, missing transverse momentum and no

electrons or muons with p T > 20 GeV. Data recorded by the

ATLAS experiment a the LHC, corresponding to an integrated

transverse luminosity of mass 1.04for fbthe −1

signal region events

seen between the numbers of events observed in the five signal

regions and the numbers of events expected from SM sources.

The exclusion limits placed on non-SM cross sections imposeThe results are interpreted in both a simplified model con-

Thursday, November 10, 11


havior of the third generation of values for the sneutrinos which in turn induce 2 a mixing

he , for behavior which dedicated of the third analyses generation are of between values neutrinos for theand sneutrinos neutralinos, whichthus in turn providing induce a phe-

sneutrinos betweenwhich neutrinos viable turn and alternative induce neutralinos, a mixing the thus origin providing of neu-

a phe-

a mixing

ptons, E

Miss T +b-jets+1 lepton

third [23] isgeneration for usedwhich to calculate dedicated of values theanalyses SUSY for the arenomenologically

JET um icated [23] the analyses is electroweak used are to calculate scale. between the For neutrinos SUSY

and nomenologically mass neutralinos, and mixing viable thus [26, providing 27]. alternative In the a phenomenologically

scale. For

to study the presented origin of neutrino

the R-parity alternative mass andviolating mixing to the[26, couplings origin 27]. ofInare neu-

thembedded study presented in

pectrum , calculate the expected athe the SUSY signal electroweak distributions interpretation

here, viable

poses, troweak SSM model thescale.

expected point For msignal 0 =500GeV, trino distributions mass andan mixing MSUGRA/CMSSM here, [26, the 27]. R-parity In the SUSY violating study production couplings presentedmodel. are embedded For a in

ich signal /CMSSM is close distributions to model the expected point mhere, 0 sensitivn,

int which them figures 0 is =500GeV, close of this to the paper. expected an MSUGRA/CMSSM sensitivters

are chosen unambiguously SUSY set ofproduction MSUGRA determined parameters, model. under For the a

bRPV tree-level parame-

=500GeV, the R-parity chosen an violating set MSUGRA/CMSSM of couplingsparameters, areSUSY embedded production the bRPV in model. parame-For a

own 24, e expected 25] in the are figures characterized sensitivthis[24,

paper. 25] and are decay characterized modes, ters by are andwell unambiguously a de-

oscillations dominance determined data scenario as described under [28] in by the Ref. fitting tree-level [29]. them The to neutralino the neutrino

of this by chosen paper. well deproduction

dels

set of MSUGRA dominance ters are parameters, scenario unambiguously [28] the by fitting bRPV determined them parame-

to under the neutrino the tree-level

ticle acterized tent for production the byfinal welland state de-decadecay content assuming modes, for that the and final alla

SUSY state oscillations particles under study. data decay asLSP described modes is unstable that in Ref. predominantly and [29]. decays The within neutralino includethe neutrinos detector[30].

through

under dominance modes, study. and scenario aLSP oscillations is[28] unstable by fitting data and decays as them described to within theineutrino

Ref. detector [29]. The through neutralino

by

reved pecific l decay state bychains. model under SUSY

assuming

In particles are study. regions

that veryon of

all massive their parameter LSP SUSY

decay isand

particles unstable chains. MPO Such Inand CR regions and decays

SUSY of VSC

modes along parameter particles

within CR, that

Czech on

the predominantly

their Republic; detector presence

decay chains. DNRF, of through neutrinos include

InDNSRC

regions

neutrinos of

SUSY

parameter

[30].

splittings ot achieve alla specific SUSY space between a final particles model with states, state small arethe with mass very modelling decay splittings leptons, massive modes between and

that decay Lundbeck states, predominantly Such chains space the decays Foundation, modelling such withalong small as include ˜χ Denmark; ± mass with → lν splittings the neutrinos ˜χ ARTEMIS, 0 presence leadbetween to[30].

significant of European neutrinos states, themiss-

ing signal IN2P3-CNRS, transverse with decay significance. MPO ofthe initial chains CRpresence momentum. and CEA-DSM/IRFU, state This such VSC radiation of asCR, neutrinos ˜χ ± However, can Czech →France; affect lν ˜χ in

modelling in SUSY

der re

les can considered very

on

to affect their

achieve of massive the initial decay

here signal astate chains.

final and contain significance. radiation state

In regions

Such a chargino with can This decays

of affect leptons,

parameter the Union; along

Republic; 0 the this SUSY lead GNAS, signal model toDNRF, Georgia;

such used BMBF, modification. as ing toand ˜χ DFG, optimize modelling ± transverse Lundbeck →HGF, lν ˜χ is the MPG 0 taken Foundation, momentum. lead selection. and from toAvH significant HERWIG Denmark; Foundation, Only However, without the miss-

ARTEMIS, Germany; muon this modification. model selection European was not

elightest eutralinos, ˜χ contain radiation ± → W neutralino with (∗) can In a chargino the ˜χ affect 0 the . limit The assumption the (LSP) of chargino signal light ing and neutralinos, that significance. transverse arises theon-shell

GSRT, with This

momentum. the considered Greece; assumption used Union; to In ISF, IN2P3-CNRS, the optimize in However, that MINERVA, limit this theof analysis the light this CEA-DSM/IRFU, GIF, selection. neutralinos, model since DIP and was Only Benoziyo with thenot

France; leptonic the assumption Cen-

muon GNAS, decays selection Geor-

that the

significant significance. wasDNSRC

notmiss-

This

lmall odels st HERWIG state neutralino mass considered modelling without splittings leptons, (LSP) modification. is here between taken and contain from states, an decay on-shell HERWIG athe chains chargino modelling without

directly taken squark SP) son: and from ˜χ ± produced coloured or →an HERWIG aW on-shell gluino, (∗) and sparticles without ˜χ 0 decay . via The modification.

are directly used one chargino directly of to the optimize produced arises ter, of Israel; and the isINFN, LSP, gia; decay considered selection. coloured BMBF, the Italy; directly electron sparticles DFG, MEXT in Only to this HGF, and channels the are analysis MPG JSPS, directly muon and Japan; are since produced selection AvH highly CNRST, in Foundation, the and suppressed Morocco;

in favor this FOM of of GSRT, analysis jets LSP, NWO, Greece; µ- ˜χ andτ-producing since 0 1,thelimitsonthegluinoandsquarkmassesareap-

Netherlands; ISF, electron MINERVA, RCN, modes. GIF, Norway; DIPScenarios MNiSW,

Benoziyo lead-

Cen-

leptonic decay Germany; directly in decays to

it nthegluinoandsquarkmassesareapand

rticles 875are GeV proximately directly respectively produced 700 for GeV and squark and decay 875 or directly GeVPoland; respectively ing to to GRICES ter, aproximately long Israel; forand squark lifetime INFN, FCT, 700 orPortugal; Italy; (cτ GeVMEXT MERYS 875 GeV JSPS, (MECTS), respectively Japan; Ro-

CNRST, for squark Mo-or

thelimitsonthegluinoandsquarkmassesareap-

TeV, rarchy rising corresponding to 1075 masses GeVbelow ifto sequential

> leptonic channelsdecays

are highly suppressed in

of The considered:

ofalight chargino jets neutralinos, orarises

˜χ a 0 1,thelimitsonthegluinoandsquarkmassesareap-

gluino, with isassumption via considered one ofthat odels ino, via considered: one of the of the LSP, the electron favorchannels of the µ-are andτ-producing highly ∼ 15suppressed mm) of modes. the LSP Scenarios are notlead-

2squarks

TeV, risingmania; to 1075 considered

MES GeV rocco; gluino to

of if here. the Russia

aFOM long masses squarks and lifetime below NWO, ROSATOM, 2Netherlands; (cτ TeV, rising Russian to RCN, 1075 Federation; Norway; GeV if the MNiSW, squarks

o-neutralino ss d to be mass-degenerate. and Limits gluinos on are gluino assumed These and limits

stop be mass-degenerate. masses, JINR; MSTD, assuming

700hierarchy GeV and 875 corresponding decay, GeVhereafter respectively tocalled

sequential

> in

favor of µ- andτ-producing modes. Scenarios

for squark or Poland; Serbia; These gluinos GRICES limits MSSR, are Limits and assumed Slovakia;

∼ 15 mm) leading

to (MECTS), These masses, Ro-

limitsthree

hanged es del, below the if2remain the decay m( TeV, ˜χ 0 ) = 60 GeV, m( ) = 2m( ),

of the LSP are not

FCT, on gluino to Portugal; be ARRS mass-degenerate. and MERYS and neutralino MVZT,

1 rising mass essentially chain to is raised 1075 ˜q unchanged →GeV as q ′ high ˜χ ± a long lifetime considered (cτ here.

nding rgino-neutralino to sequential decay, hereafter if the →if called

> the squarks Slovenia; ˜χ 0 DST/NRF, ∼ 15 mm) of the LSP are not

Southbody Africa; decay MICINN, g → Spain; t t SRC and

considered 1 massmania; isremain raised MES as essentially high of Russia unchanged and ROSATOM, if the ˜χ 0 1 Russian mass is raised Federation; as high

are of model, assumeda specific to BR(g the 200 toSUSY-breaking have be decay GeV. → mass-degenerate. t aIn t) chain 100% the = BR(t case scenario, ˜q branchdis

only assumed ˜q first- → q and ′ to ˜χ ±

have second-generation

→ 11% tan β = 10, A 0 = 0, µ>0, the

of → aThese b specific q ′ ˜χ ± here.

~

~

ay, hereafter called ~ ~ ) Wallenberg limits = →SUSY-breaking 100%, JINR; Foundation, and as 200 MSTD, scenario, GeV. Sweden; In Serbia; the case SER, MSSR, of aSNSF specific Slovakia; andSUSY-breaking Cantons ARRS of

III. THE ATLAS DETECTOR

MVZT, scenario,

Achain tially withunchanged tani.e. β BR( = CMSSM/MSUGRA 10, if→ Athe 0 = ˜χ 0 0, l µ>0, nu) = with the Bern and Geneva, Switzerland; NSC, Taiwan; TAEK, Turkey;

1 amass 100% is raised branchn,

end and squark-antisquark 100% only first- branch-

and production second-generation is

as high Slovenia; i.e. CMSSM/MSUGRA DST/NRF, South with Africa; tanMICINN, β = 10, ASpain; 0 = 0, SRC µ>0, andthe

60 InGeV the case for limit low of on avalues specific m 1/2 reaches ofSUSY-breaking m 0 ,andequal 460 GeV for scenario,

STFC, low values the Wallenberg Royal oflimitm 0 ,andequal Society

III.

on mFoundation, 1/2

and

THE

reaches Leverhulme

ATLAS

460 Sweden; GeVTrust, DETECTOR

for SER, low United SNSF values Kingdom;

below DOE ATLAS THE

and of mCantons 0 ,andequal of

III.

os /MSUGRA are excluded mass with squarks below tan β 950 and = GeV. 10, gluinos AThe are usexcluded 950 andATLAS GeV. NSF, The United use States dom; of America. DOE and NSF, United States of America.

is is achieved by setting all 0 = other 0, µ>0, the Bern mass [31] squarks Geneva, is DETECTOR

aand Switzerland; particle gluinos are physics excluded NSC, Taiwan; detector belowTAEK, 950with GeV. Turkey; The a

dark second-generation

and squark-antisquark production is

use

sitive to larger of signal jet multiplicities selections sensitive thaninto larger The jet crucial multiplicities computing thanin support from all WLCG partners is

2 reaches 460 GeV for low values of m 0 ,andequal

forward-backward STFC, ATLAS of signal the Royal selections [31] symmetric Society is asensitive particle andcylindrical Leverhulme to larger physics jetTrust, geometry multiplicities detector Unitedand

Kingdom;

0 [5] . particle coverage The gratefully, DOE hasfive improved and sig-

physics inNSF, insolid particular the symmetric United ATLAS detector angle States from [32]. reach cylindrical of CERN with America. at The large and inner mthe

geometry 0 . The detec-

five sig-

and

with

. asses, This including is achieved those by of setting third gen- all other

thanina

squark production is

sTLAS and gluinos reach [5] has are at large excluded improved m 0 . below The the five ATLAS 950sig-

set limits sensitive nal onregions σ new to = larger are σAɛ, used jet fornon-SM multiplicities forward-backward to set limits on thanin

GeV. reach The

acknowledged [31] at use near large is forward-backward 4π am ticle by , tosetting masses, multi-TeV all including other values. those Thisof model third genuarks,

g

ections

ATLAS σtor new = (ID) Tier-1 near symmetric σAɛ, nal The consists 4π facilities fornon-SM regions crucial coverage cylindrical are at of computing TRIUMF used a silicon to solid set support (Canada), geometry limits pixel angle from ondetector, [32]. NDGF σall and new WLCG = The (Denmark,

Norway, Sweden), and aCC-IN2P3 (France), KIT/GridKA

σAɛ, ainner partners silicon fornon-SM detector

acknowledged solid cross-sections (ID) detector angle consists gratefully, [32]. (σ)forwhichATLAShasanacceptanceA (SCT), of The a in silicon and inner particular a transition pixel detec- from detector, CERN radiation and a silicon the and a

is

oved hichATLAShasanacceptanceA

by those three to

the cross-sections

ofree multi-TeV third parameters: gen-valuesvalues. m 0)/(m by November three This10, −free model 11

reach (σ)forwhichATLAShasanacceptanceA

m˜q This

at large near mand , m

a 0 . 4π The ˜χ

0,

coverage

model

five sig- microstrip in

−rized Thursday,

m 0). parameters: m˜q , m 0,

MPO CR and VSC CR, Czech Republic; DNRF MPO

and Lundbeck Foundation, Denmark; ARTEMIS, and

Union; IN2P3-CNRS, CEA-DSM/IRFU, France; Uni GN

gia; BMBF, DFG, HGF, MPG and AvH Foundation gia;

GSRT, Greece; ISF, MINERVA, GIF, DIP and Ben GSR

ter, Israel; INFN, Italy; MEXT and JSPS, Japan; ter, CN

rocco; FOM and NWO, Netherlands; RCN, Norway rocc

Poland; GRICES and FCT, Portugal; MERYS (ME Pola

mania; MES of Russia and ROSATOM, Russian manF

JINR; MSTD, Serbia; MSSR, Slovakia; ARRS JINR a

Slovenia; DST/NRF, South Africa; MICINN, Spain Slov

Wallenberg Foundation, Sweden; SER, SNSF and Wal

Bern and Geneva, Switzerland; NSC, Taiwan; TAE Bern

STFC, the Royal Society and Leverhulme Trust, STF Un

dom

The crucial computing support from all WLCGT

acknowledged gratefully, in particular from CER ackn

ATLAS Tier-1 facilities at TRIUMF (Canada), ATL ND

mark, Norway, Sweden), CC-IN2P3 (France), mar K

22


E

Miss T +2 photons

– Variable next-to-lightest

Targeting the direct or gluino mediated – Variable production NLSP lifetime

of a pair of bino-like NLSP decaying from into the gravitino coupling

and photon


Possibility of photons + E miss T

signatures

Selection: two photons of pT > 25 GeV, ET Miss >

125 GeV.

Three categories of backgrounds:

– SUSY is broken in a hidden sector

QCD (di-jet, jet-gamma, gamma gamma) with

fake ET Miss . Estimated with a loose photon

selection, normalized to gamma gamma data

with ET Miss < 20 GeV

– Communicated by messenger fields to the MSSM via the Standard

Model gauge interactions

– Gravitino is the lightest

superpartner (LSP)

superpartner (NLSP)

http://www-cdf.fnal.gov/physics/exotic/r2a/20080729.gammajet/photonjets.html

Oct 20, 2011 Daniel Damiani – SUSY Searches with Photons in ATLAS 2

e gamma (W or semileptonic top pairs) with

real ET Miss , with the electron misidentified as

photon. Estimated from an egamma sample, to

which the electron -> gamma misidentification

probability (measured from a Z ee sample) is

applied.

Irreducible: Zgg, Wgg. From MonteCarlo.

5 events observed in signal region

expected = 4.1 ±0.6 (stat.) ±1.6 (syst.)

Thursday, November 10, 11

23


E T

Miss

+2 photons limits

Universal extra

dimensions

1/R > 1226 GeV for

⋀R = 20

SPS8

Minimal GMSB model (*)

with heavy squark and

gluinos, so that gaugino

EW production dominant.

General Gauge Mediation

m(g) > 806 GeV for bino masses larger

than 50 GeV

First limit from LHC:

⋀ > 145 TeV

* Eur. Phys. J. C25 (2002) 113

Thursday, November 10, 11

24


Long lived particles and R-parity

violation searches

Long lived particles are predicted in many scenarios: weak R-partity violating (RPV)

couplings, long-lived NLSP due to small NLSP-LSP mass splitting or weak coupling

to gravitino LSP, split susy with heavy scalars, ...

If coloured, they would hadronize with quarks (R-hadrons).

I will present four searches for long lived particles

For particles decaying in the Inner Detector: a search for secondary decay vertices

and one for disappearing tracks

Two searches for non relativistic heavy particles (R-hadrons or sleptons)

Also I will show the search for an eμ resonance, which is relevant for some RPV

scenarios

Thursday, November 10, 11

25


arXiv:1109.2242v1 [hep-ex] 10 Sep 20

supersymmetric particles in an R-parity-violating scenario as a function of the neutralino lifetime. Limits are

for di↵erent squark and neutralino masses, enabling extension of the limits to a variety of other models.

Displaced vertices search

1. Introduction

Various scenarios of physics beyond the standard model

predict the production at the Large Hadron Collider

Target: heavy

(LHC)

particle

of heavy

decaying

particles

in

with

charged

lifetimes

particles

that maywith be of

ct

order picoseconds to about a nanosecond. An example

of to such tens a scenario of cm, isand gravity-mediated produced with supersymmetry (or decaying

between ~1 mm

into) an high-pT (SUGRA) muon with R-parity violation (RPV), where current

limits on RPV couplings [1] allow for the decay vertex of

the lightest supersymmetric particle to be within the range

Ask one muon accessible with pT to > collider-based 45 GeV and particle at least detectors. one In 4-track gaugemediated

chi square supersymmetry < 5, radius models, between the next-to-lightest 40 and 180 su-mmpersymmetric

particle may be long lived due to suppres-

vertex with fit

z coordinate less than 300 mm, distance from primary vertex at

sion of its decay by the large supersymmetry-breaking

least 4 mm, veto scale position [2]. Additional matching scenarios high allowing density for detector such a signature

conversions include split-supersymmetry and hadronic [3], interactions),

hidden-valley [4],

material (to reject

dark-sector gauge bosons [5], stealth supersymmetry [6],

vertex mass larger than 10 GeV.

or a meta-stable supersymmetry-breaking sector [7].

Searches for related signatures have been performed at

the Tevatron with p s =1.96 TeV p¯p collisions. The D0

Estimate background as the product of the probability of

having an high pT muon and one such vertex, from MC.

Tracking and vertex description in MC validated on data.

collaboration has searched for a long-lived neutral particle

decaying into a final state containing two muons [8] or a b¯b

pair [9]. No signal was observed, and limits were computed

in the context of RPV and hidden-valley model scenarios.

In this letter, we report the results of a search for a

heavy particle decaying into several charged particles at a

distance of order millimeters to tens of centimeters from

the pp interaction point, in events containing a muon with

high transverse momentum (p T ). In the SUGRA scenario,

this signature corresponds to the decay of the lightest supersymmetric

particle due to non-zero RPV couplings 2ij ,

0

via a diagram such as the one shown in Fig. 1. However,

it may also be the result of other models with heavy, longlived

particles that decay into or are produced in associa-

Control plots done with all requirements except material veto, and

number of tracks, and with vertex mass cut reversed.

Thursday, November 10, 11

~

0 µ ~χ

λ


An RPV example

Figure 1: Example of a diagram of a new massive parti

as the lightest neutralino) decaying into a muon and tw

virtual smuon, with RPV coupling 0 2ij .

2. The ATLAS detector

33 pb -1

arXiv:1109.2242

submitted to PLB

The ATLAS detector [10] comprises a trackin

tector (ID) system, a calorimeter system, and an

muon spectrometer (MS).

The ID operates in a 2 T magnetic field an

tracking and vertex information for charged part

pseudorapidity range |⌘| < 2.5, where ⌘ ⌘ l

and ✓ is the polar angle, defined with respect to

drical symmetry axis (the z axis) of the detector

radii, high-resolution pattern recognition capab

tained using silicon pixel layers and stereo pair

microstrip layers. The pixel system comprises th

layers, and three forward disks on each side of t

tion point. Of particular significance to this an

the barrel pixel layers, which are positioned at ra

88.5, and 122.5 mm. The silicon microstrip trac

has four barrel layers, and nine forward disks on

At larger radii, a transition-radiation tracker (T

posed of straw-tube elements interleaved with 26

µ

2ij

q j

q

i


Displaced vertices analysis

results

No events are observed in the signal region,

with an expected background of less than

0.03

Limits derived for various squark and

neutralino masses.

Thursday, November 10, 11

27


1.02 fb -1 28

Disappearing track search

In anomaly mediated models the lightest

chargino decays into a soft pion and the

neutralino, with a lifetime of order of ns.

Selection:

ET Miss > 130 GeV, ≥ 1 jet with pT > 130

GeV, ≥ 2 other jets with pT > 60 GeV (from

gluino decay), no electron or muon with pT >

10 GeV

The highest pT track is isolated, well

reconstructed in Pixel and SCT, points to

barrel TRT fiducial volume, has no hit in

outer TRT ring (chargino track)

Background pT spectrum obtained from data:

Hadrons interacting in the TRT: control

sample of non-interacting hadrons

Badly reconstructed tracks: low ETMiss, no

Pixel hit tracks

χ ±

1

χ 0

1

~

g

g

~

→ χ ±

1

q q

0

χ ± → χ

1 1

π ±

Number of hits in

3 rd TRT layer

Thursday, November 10, 11


Disappearing track search

results

Effective cross section limit as a

function of the track p T cut

The pT spectrum of selected track candidates (above)

is fitted with the background template from control

samples plus the signal template from MC.

Fit is consistent with no signal.

Limits in chargino mass and

lifetime plane.

First limits beyond LEP!

Thursday, November 10, 11

29


Muon spectrometer based

37 pb -1

PLB 703,428

search for slow particles

Signature is speed v/c < 1. Mass reconstructed from momentum and velocity.

Muon-triggered events, time of flight is measured from muon and hadron

calorimeters. Search for long lived scalar leptons and R-hadrons (the latter are

allowed to be neutral before interacting the calorimeters, i.e. an Inner Detector track

is not required)

Background estimate based on measured velocity resolution function

Limits:

• slepton, GMSB: 136 GeV

• slepton, electroweak

production: 110 GeV

• R-hadron gluino: 530-544

GeV

Thursday, November 10, 11

30


Muon agnostic

34 pb -1

PLB 701,1

search for slow particles

Using the pixel dE/dx and the tile time of flight to measure particle velocity

Background is from instrumental resolution tails in these variables. Since they are

uncorrelated, resolution function can be measured from data.

Limits derived on the mass of long-lived scalar bottom (294 GeV), top (309 GeV) and gluino

(562-584 GeV).

Thursday, November 10, 11

31


alenew 2 shows physics the signal. numbers of observed and predicted > 600 GeV 3 2.4 ± 0.4

ound e numbers events of observed in eleven and high predicted eµ mass regions. Good

650 GeV 1 1.49 ± 0.31

> 650 GeV 1 1.49 ± 0.31

nent eleven is found high eµ for massall regions. massGood

regions and no statisti-

700 GeV 0 1.07 ± 0.25

> 700 GeV 0 1.07 ± 0.25

1.07 fb -1

ignificant

for all massdata regionsexcess and noisstatisti-

a excess is observed. Limits are set

observed.

eμ resonance

Limits are set

search

Fig.

arXiv:1109.3089

Fig. 1

contributions of new physics processes of newto physics the highprocesses to the high

submitted to EPJCL tions. tion

egion o scenarios: fromthe two production scenarios: of ˜ν the τ in production of ˜ν τ in

m Z ′

V SUSY model and of an LFV Z ′ m

in The extra-gauge

i, j, k =1, 2, 3 refer to the fermion Z ′ =

el and of an LFV Z ′ in extra-gauge The indices i, j, k =1, 2, 3 refer to the fermion generation are are us

odels. Possible signals: Z’ with lepton numbers. flavour violations, The Thecoupling RPV constants SUSY with λλscalar satisfy satisfy tau λ ijk

λdecay

ijk = = −λ −λ jik jik . .

process d ¯d

is is assu

˜ν τ → eµ in a SUSY RPV model is

→ ˜ν τ → eµ in a SUSYOnly RPVthe model tau tau

is sneutrino is isconsidered in inthis thisLetter since since the the LF

V sneutrino couplings allowed in the Production and decay

red. The RPV sneutrino couplingsstringent allowed limits in thealready exist on onthe theelectron sneutrino and and only onlys

rangian are 1 2

mmetric Lagrangian λ ijk ˆL i ˆLj Ê k +λ ′ ˆL ijk i ˆQj ˆDk

are 1 2

Two relevant RPV couplings: λ ijk ˆL

, Relevant

muon RPV

i ˆLj Ê k +λ ′ sneutrino ˆL

Lagrangian

By all ijk i ˆQj ˆDk ,

′ L Q are lepton and quark SU(2) for (˜ν τproduction, to douperfields,

and The E and ATLAS D Collaboration: denote the singlet Search for fields τ is the T

τ is the lightest supersymmetric particle, the Th

¯d)

[1]. By fixing all RPV couplings except

the lepton and quark SU(2) douλ

′ E and D denote the singlet fields 311 (˜ν τ to d ¯d) andλ 312 312 for (˜ν (˜ν τ decay τ to toeµ) eµ) tozero,andassuming

that ˜ν ˜ν and down type quarks, respectively.

a heavy particle decaying into an electron and a muon

rged leptons Selection andis down exactly type one electron contributions quarks, and respectively. one muon to tothe with eµ

pT

eµ final > 25 state GeV

originate from the the˜ν ˜ν new newh

τ τ

only. The cross section is is0.154 pb pbfor for m˜ντ =650GeV, range

Table 1. Estimated backgrounds in the selected sample, together

with the observed event yield. Theistotal integrated lu-

eµ final state. To calculate the efficiency and ac

the production of vector particles that can dec

Data-driven multi-jet estimate λ from ′′ loose lepton control 312 samples; other processes from

311 =0.10 and λ 312 =0.05 [24]. The total decay width pends

minosity MonteCarlo.

is

is 1.07 fb −1 Γ˜ντ ′2

.

311 312 Z ′ is assumed

τ that

Γ˜ντ =(3λ ′2

311 +2λ2 312 )m˜ν τ

/16π. Using couplings that numb

are to have same quark and le

consistent with the thecurrent limits, the thedecay width widthis

nal

is nal ev

plings as the SM Z except a non-zero Z ′ to eµ

Process Number of less events than 1 GeV for for m˜ντ

1 TeV, is well below the per

m˜ντ = 1 TeV, which is well below the per li

which is assumed to be the same as the Z ′ to ee

t¯t 1580 ± contribution 170 from fromdetector resolution.

The cross MC

section is 0.61

MCsamples pbsamples with metho

for m

with

Jet fake 1180 ± 120

Z ′

˜ν

=700GeV

˜ν τ masses τ ranging from from0.1 Z/γ ∗ samples 0.1to with to2 2TeV Z TeV

→ ττ 750 ± 60

′ are

masses aregenerated generatedwith

cross

ranging from with cros

0.7 to 2

herwig herwig [16,25].

and

[16,25].

ando

WW 380 ± 31

generated with pythia.

An

Single top 154 ± 16 An



resonance

resonance

also

also Both

appears

appears ˜ν τ and

in

in Z

models ′ models samples

containing

tion

containing are processed

tion

o

th

aheavyneutralgaugeboson,Z

W/Z + γ 82 ± aheavyneutralgaugeboson,Z 13

standard chain ′ ′ [26], of [26], the with

with ATLAS non-diagonal

by

non-diagonal simulation and by

AT

re

lepton flavor couplings.

WZ 22.4 ± lepton 2.3 flavor couplings. tion. Rare The Rareoverall muon decay

muonproduct searches

decay searches of acceptance have

have and 2 effi

placed extremely stringent

ZZ 2.48 ± placed 0.26 extremely stringent 36% forlimits m˜ντ limits = on 100the on the GeVcombination combination and increases of

of to 64%

2 Th

T

m˜ντ +

m˜ντ

Total background 4150 ±

the

the 250mass and the coupling

mass and the coupling

1 TeV. toThe ee and

to ee

corresponding eµ such

and eµ in such

number models [2].

models

is

[2].

∼ 60% 11 GeV fo

Data 4053 The eµ searches at hadron mass mcolliders Z ′ =700GeVtom are not able Z ′ = to2match

TeV. The pred

11 G

m˜ντ +

The

sensitivity

eµ searches

of dedicated

at hadron colliders are not able to match m˜ντ

distributions µ → efor conversion a ˜ν τ withexperiments.

m˜ντ =650GeVand If m˜ντ

Athe limit sensitivity on the production of dedicated

m Z ′ = cross 700

µ →section GeV

e conversion

aretimes also shown branching experiments.

Fig. ratio

A limit to eµ on is the placed production on the Z cross ′ -like boson model times to branching represent ra- statist The

1. The If m

Thursday, November 10, 11

32

D


Table 2. Estimated total backgrounds in the selected sample,

Table 2. together Estimated with total the backgrounds observed event in theyields selected forsample,

11 high eµ mass

together with regions. the observed event yields for 11 high eµ mass

regions.

m eµ Data SM prediction

m eµ

> 200

Data

GeV

interpretation

286

SM prediction

288 ± 22

> 200 GeV

> 250

286

GeV 152

288 ± 22

136 ± 11

> 250 GeV 152 136 ± 11

> 300 GeV 70 67 ± 6

> 300 GeV 70 67 ± 6

> 350 GeV 35 34.0 ± 3.0

> 350 GeV 35 34.0 ± 3.0

> 400 GeV 22 17.7 ± 1.7

> 400 GeV 22 17.7 ± 1.7

> 450 GeV 10 10.5 ± 1.2

> 450 GeV 10 10.5 ± 1.2

> 500 GeV

> 500 GeV

7

7

6.8 ± 0.9

6.8 ± 0.9

> 550 > 550 GeV

3

3

4.3 ± 0.6

4.3 ± 0.6

> 600 GeV> 600 GeV 3 3 2.4 ± 0.4 2.4 ± 0.4

> 650 GeV> 650 GeV 1 11.49 ± 0.311.49 ± 0.31

> 700 GeV> 700 GeV 0 01.07 ± 0.251.07 ± 0.25

eμ resonance search 10

3

0 200 400 600

0 200

2

400 600 800 100

2

1

1

The indices Thei, indices j, k =1, i, 2, j, 3k refer =1, 2, to3the refer fermion to thegeneration

fermion generation are used for are the used RPVfor˜ν τ the model. RPVThe ˜ν τ mode prod

numbers. numbers. The coupling The coupling constants constants λ satisfy λ ijk satisfy = −λλ jik ijk . = is−λ assumed jik . isto assumed be the current to be the published currentl

Only theOnly tau sneutrino the tau sneutrino is considered is considered in this Letter in this since Letter thesince

LFV Z the ′ model LFV[8]. Z ′ The model ratio [8]. plot Theat

ra

stringent Most stringent limits already limits exist already on the on the couplings exist electron the for sneutrino electron sneutrino and masses only > and 270 statistical GeV only uncertainties.

statistical uncertainties.

muon sneutrino muon sneutrino [1]. By fixing [1]. By all fixing RPV couplings all RPV couplings except except

λ ′ For λ ′ 311 = (˜ν 0.10, τ to d ¯d) 311 (˜ν τ to d ¯d) andλ 312 = andλ (˜ν 0.05, τ to 312 limit eµ) (˜ν tozero,andassuming

that ing ˜ν τ is that the˜ν lightest τ is thesupersymmetric lightest supersymmetric particle, the The m

τ is 1.32 eµ) TeV tozero,andassum-

particle, the eµ spectrum The m eµ

is spectrum examined is for ex

contributions contributions to eµ tofinal the state eµ final originate state originate from the from ˜ν new heavy

the ˜ν new particle. heavyFor particle. each assumed

τ

For eac

τ

only. Theonly. crossThe section crossissection 0.154 pb is 0.154 for m˜ντ pb=650GeV,

range 100

for m˜ντ =650GeV, range GeV 100 to 2 GeV TeV, toa 2search

TeV,

λ ′ 311 =0.10 λ ′ and 311 =0.10 λ 312 and =0.05 λ [24].

312 =0.05 The [24]. totalThe decay total width pends on the

decay width pends simulated on the simulated eµ mass resolu eµ m

is Γ˜ντ =(3λ is ′2

311 Γ˜ντ =(3λ +2λ2 312 ′2

311 )m˜ν +2λ2 τ

/16π.

312 )m˜ν Using

τ

/16π. couplings Using couplings that number of

that number observed of and observed predicted and ba pr

are consistent

are consistent

with the

with

current

the

limits,

current

the

limits,

decay

the

width

decay

is nal events

width is nal

in

events

each search

in each

range

search

are

r

u

per limit on σ(pp → ˜ν ) × BR(˜ν

33 →

Thursday, November 10, 11

Events / 25 GeV

Data/SM

2

10

10

1

-1

10

-2

10

Events / 25 GeV

Data/SM

10

10

3

2


10

1

-1

10

-2

10

ATLAS

s = 7 TeV

-1

Ldt = 1.07 fb

ATLAS


s = 7 TeV Data 201

Total Bkg

Ldt = Top 1.07 fb

*

Z/γ τ→

0 200

0

400

200

600

400

800

600

100

Fig. 1. Observed Fig. 1. and Observed predicted andeµ predict inva

tions. Signal tions. simulations Signal simulations are shown for are ms

m Z ′ =700GeV.Thecouplingsλ m Z ′ =700GeV.Thecoupling

′ 311 =0


Conclusions ?

Abstruse Goose gets it right ?

No evidence of non-SM

contributions has been found in

1 fb -1 of collision data and a

large variety of final states

SUSY limits on squarks and

gluinos are now approaching

the TeV scale

2

Thursday, November 10, 11

34


Outlook

These results rule out the easy scenario of sub-TeV squark (first generations) or gluino

with a light LSP.

With 5 fb -1 now on disk, we are looking at many other possibilities:

Direct production of scalar bottom, top, slepton, and gaugino

Compressed mass spectrum

Refining consolidate searches, like moving from cut-and-count in one bin to shape

analysis, work on systematics etc., to further push up sensitivity

We haven’t given up, and we are still optimizing our searches for discovery, not

exclusion... stay tuned for more results with full 2011 data set!

Thursday, November 10, 11

35


Backup slides

Thursday, November 10, 11

36


Performance and Standard Model

measurements

Multi jet cross section

arXiv:1107.2092

W+jet cross section

Phys. Lett. B698, 325

Events / 2 GeV

3

10

2

10

The ATLAS Collaboration: Performance of Missing Tra

Missing Et in Z(ee) candidates

arXiv:1108.5602


Ldt=36 pb

s = 7 TeV

-1

ATLAS

Data 2010

MC Z → ee

MC ttbar

MC WZ

10

MC WW

1

0 20 40 60 80 100 120 140

miss

E T

[GeV]

The new pysics searches

presented here are possible

because of the excellent

performance of our detector

and the understanding we

achieved of Standard Model

processes.

Thursday, November 10, 11

tt+jets, ATL-CONF-2011-142

Jet 600 energy scale uncertainty for central jets

Data 2010

ATL-CONF-2011-032 ATLAS

500

Events / 0.2 rad

400

300

200

100

MC Z → ee

MC all backgrounds

-3 -2 -1 0 1 2 3


Ldt=36 pb

s = 7 TeV

-1

miss

φ

[rad]

Fig. 5. Distribution of ET

miss (top) and φ miss (bottom) as measured in a da

from Monte Carlo simulation is superimposed and normalized to data, afte

The sum of all backgrounds is shown in the lower plots.

37


AMSB search backup plots

Hadron track control

sample fit

Bad track control

sample fit

Thursday, November 10, 11

38

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