Results of the OPERA experiment - Infn

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Results of the OPERA experiment - Infn

Results of the OPERA experimentGiovanni De LellisUniversity “Federico II” and INFN NapoliOn behalf of the OPERA CollaborationOn behalf of the OPERA Collabora2on 26/03/13 Giovanni De Lellis, LNGS Seminar 1


Outline of the talk• The OPERA experiment and its detector• The analysis chain• Charmed hadron production• Oscillation physics results• Background studies• Significance26/03/13 Giovanni De Lellis, LNGS Seminar 2


CNGS BEAM AND LNGS 26/03/13 Giovanni De Lellis, LNGS Seminar G. De Lellis - Fermilab - 4 June 20107


CNGS beam: tuned for τ-appearance at LNGS730 km away from CERNCERN"L = 730 km"LNGS"T flight = 2.44 ms"26/03/13 Giovanni De Lellis, LNGS Seminar G. De Lellis - Fermilab - 4 June 20108


Neutrino Beam ParametersBeam parameters (GeV)17(νe+νe)/νμ 0.9% *νμ/νμ 2.0% *ντ prompt Negligible* Interaction rate at LNGS26/03/13 Giovanni De Lellis, LNGS Seminar 9


LNGS of INFN, the world largest underground physics laboratory:~180’000 m 3 caverns’ volume, ~3’100 m.w.e. overburden, ~1 cosmic µ / (m 2 x hour),experimental infrastructure. Suitable to host detector and related facilities, caverns orientedtowards CERN.OPERA 26/03/13 Giovanni De Lellis, LNGS Seminar G. De Lellis - Fermilab - 4 June 201010


CNGS beam structureDedicated mode or 5 cycles + LHC (during filling)Shared operation FT + 4 CNGS + LHCShared operation no LHC filling (5 CNGS+ FT)High CNGS duty cycle26/03/13 Giovanni De Lellis, LNGS Seminar 11


Final performances of the CNGS beam after fiveyears (2008 ÷ 2012) of data takingYear Beam daysP.O.T.(10 19 )2008 123 1.742009 155 3.532010 187 4.092011 243 4.752012 257 3.86Total 965 17.97p.o.t. (10 18 )2008 2009 Record performances in 2011 Overall 20% less than the proposal value (22.5) 2010 2011 2012 date26/03/13 Giovanni De Lellis, LNGS Seminar 12


DETECTORS AND FACILITIES in opera8on: A very complex experiment… 26/03/13 Giovanni De Lellis, LNGS Seminar G. De Lellis - Fermilab - 4 June 201013


Two target super-modules, each with an iron spectrometer formuon detection (BG rejection and tau à muon decay channel)26/03/13 Giovanni De Lellis, LNGS Seminar G. De Lellis - Fermilab - 4 June 201014


SCINTILLATOR STRIPS TARGET TRACKER AND BRICK TRAYS> 5 p.e. for a m.i.p. ~ 99% detec2on efficiency ⇒ trigger posi2on accuracy: ~ 8 mm angular accuracy: ~ 15 mrad mechanical structure: brick trays: only 0.5% of target mass σ = 8 mm26/03/13 Giovanni De Lellis, LNGS Seminar G. De Lellis - Fermilab - 4 June 201015


Identification of the interaction brick: iterative process(1.6 bricks involved in the analysis of one event)ν µGiovanni De Lellis, LNGS Seminar 16 cmcm26/03/13 Brick identified (top and side view)


THE MAGNETIC SPECTROMETERS• 1.55 T magnetic field bendingparticles in the horizontal plane• 24 slabs of magnetized ironinterleaved with 24 RPC planes• 6 drift tube stations for precisionmeasurement of the angulardeflection• momentum resolution:20% below 30 GeV26/03/13 Giovanni De Lellis, LNGS Seminar G. De Lellis - Fermilab - 4 June 201017


Events-110-210-31018Events24022020018016014012010080604020Performances of the electronic detectorNew Journal of Physics 13 (2011) 053051Momentum x charge for µQE + RES-40 0 -30 -20 -10 0 10 20 30 400 0.1 0.2 0.3 0.4 0.5 0.6 0.7p x charge (GeV/c) 110.8 0.9 1Reconstructed Bjorken-yFigure 7. Muon charge comparison (momentum ⇥ charge): data (black dots witherror bars) and MC (solid line) are normalized to one.nfirmation of this hypothesis. Once again, if a lower limit on the absolute value 60Events120Figure 11. Bjorken-y variable reconstructed in data (dots with error bars) andEnergythe wrong determination of the muon charge is smaller than 2%. The chargeefficiency is also reduced at low momentum. In this case, the 3D track identifiedbe a charged hadron and hence the measured charge is not that of the muon. Thised in MC events with the final state including a muon and negligible hadronicDISNC00 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1Reconstructed Bjorken-yHit walls for contained events80in light grey, DIS contribution in grey and the NC contamination in dark grey.m is set at 2.5 GeV c 1 , the wrong determination of the muon charge is smalleruon momenta between 2.5 andshown.45 GeV c 1 , the fraction of events with wrong 40nation is 1.2%. The µ + to µ events ratio, within the selected momentum range,data can be directly compared with predictions based on the full MC sample:20at.)% for data, and 3.63 ± 0.13 (stat.)% for MC. Figure 7 shows the momentumistribution where for data Eand MC, both normalized to one: the2 ⌫µvalue is 23.34 for26/03/13 Giovanni De Lellis, LNGS Seminar 18 Events24022020018016014012010080604020QE + RESMC (shaded areas). The MC distributions 100 are normalized to data. The differentcontributions of the MC are shown in different colours: QE + RES contributionOn the left, all of the events with at least one muon are shown, whereas on theright, the events for which the momentum is measured in the spectrometer areis the incoming neutrino energy, E µ the energy of the outgoing muon and E hadthe hadronic energy. Bjorken-y connects the muon momentum measurement, performed in theDIS00 20 40 60 80 100number of wallsNCY-Bjorken for events with µmeasured in the spectrometer


The heart of the experiment:THE ECC TARGET BRICKSHybrid target structure. neutrino 10.2 cm (CS) 7.5 cm 10 X0 12.5 cm 1mm0.3mm(CS) LeadplateThe OPERA target consists of 150’000ECC bricks.Total 105’000 m 2 of lead surfaceand 111’000 m 2 of film surface(~ 9 million films)Total target mass: 1.25 kton57 OPERA films, 56 lead plates26/03/13 Giovanni De Lellis, LNGS Seminar 19


INDUSTRIAL EMULSION FILMS BY FUJI FILM Emulsion Layer (44 microns) Plas2c Base (205 microns) basic detector: AgBr crystal, size = 0.2 micron detec2on eff.= 0.16/crystal 10 13 “detectors” per film Emulsion Layer mip sensitivity 30 grains/100 µmintrinsic resolu2on: 50 nm devia2on from linear-­‐fit line. (2D) 20 μm electron ~100 keV high dE/dx tracks from nuclear evapora2on 26/03/13Giovanni De Lellis, LNGS Seminar 20


Brick validation by the interface filmanalysisDevelop this brick CS CS doublet alignment by Compton electrons: 2.5 micronsSo far 2’000’000 cm 2 of CS surface have been analysed in OPERA26/03/13 Giovanni De Lellis, LNGS Seminar 21


BRICK MANIPULATOR SYSTEM (BMS) Extraction of “hit” bricks in parallel with CNGS data taking (quasi-online):• initially used to fill the brick target (two twin devices at either detector sides)• fully automatic extraction of up to 50 bricks/day (neutrino interactions)26/03/13 Giovanni De Lellis, LNGS Seminar G. De Lellis - Fermilab - 4 June 201022


More than 20000 bricks manipulated for event analysis26/03/13 Giovanni De Lellis, LNGS Seminar 23


Target mass evolutiondate bricks16/07/08 14639824/06/09 14729231/05/12 13560613/03/13 133425Target loss ∼ 112 tonsBlack CS replacement-­‐9.3 % 26/03/13 Giovanni De Lellis, LNGS Seminar 24


FILM DEVELOPMENT FACILITY• 5 automated lines running in parallel, in a dark room• additional facility underground for Changeable Sheet films26/03/13 Giovanni De Lellis, LNGS Seminar G. De Lellis - Fermilab - 4 June 201025


Scanning of Changeable Sheets: several tasks accomplishedLNGS: 10 microscopes, 200 cm 2 /h Nagoya: 5 S-­‐UTS, 220 cm 2 /h European Scanning System Super-­‐UltraTrack Selector (Japan) 26/03/13 Giovanni De Lellis, LNGS Seminar 26


Interface emulsion films: high signal/noise ratio for eventtrigger and scanning time reductionCC interaction: µ track in interface filmsν µ26/03/13 Giovanni De Lellis, LNGS Seminar 27


Validation of events without µ in the final stateCS tracks: the arrow length isproportional to its slope10 cm 12.5 cm 26/03/13 Giovanni De Lellis, LNGS Seminar 28


Identification of cosmic ray µ and muons from ν interactions upstream:important to keep the TT running during the shutdownBremsstrahlung of a cosmic-­‐ray muon 72 tracksν interactionin the brick26/03/13 Giovanni De Lellis, LNGS Seminar 29


Interface emulsion filmsElectron showerpre-selectionTarget tracker hitsOne of the electron neutrinoslocated as seen after the brick analysis26/03/13 Giovanni De Lellis, LNGS Seminar 30


Track follow-up and vertex findingTrack follow-up film by film:• alignment using cosmic raytracks• definition of the stoppingpointCSdσ ~2 µm 12ν µ 1…484950515253545556572Volume scanning (~2 cm 3 ) around the stopping point26/03/13 Giovanni De Lellis, LNGS Seminar 31


Located neutrino interactionVolume (~2 cm 3 ) around the stopping pointEmulsions give 3D vector data, with micrometric precision of the vertexing accuracy. The frames correspond to the scanning area. Yellow short lines à measured tracks. Other colored lines à interpola2on or extrapola2on. 1 cm 26/03/13 Giovanni De Lellis, LNGS Seminar 32


Located neutrino interaction:film to film connection Emulsions give 3D vector data, with micrometric precision of the vertexing accuracy. The frames correspond to the scanning area. Yellow short lines à measured tracks. Other colored lines à interpola2on or extrapola2on. 1 cm 26/03/13 Giovanni De Lellis, LNGS Seminar 33


Located neutrino interaction Emulsions give 3D vector data, with micrometric precision of the vertexing accuracy. The frames correspond to the scanning area. Yellow short lines à measured tracks. Other colored lines à interpola2on or extrapola2on. 1 cm 26/03/13 Giovanni De Lellis, LNGS Seminar 34


Improved decay search procedureTrack segment26/03/13 Giovanni De Lellis, LNGS Seminar 35


Decay search: penetrating tracks discardedTrack segmentmicro-track segment26/03/13 Giovanni De Lellis, LNGS Seminar 36


Decay search: track selectionΔZ >6 mmTrack segment26/03/13 Giovanni De Lellis, LNGS Seminar 37


Decay search: electron pairTrack segmente +/ e - from an electron pair26/03/13 Giovanni De Lellis, LNGS Seminar 38


Decay search: kink topology detectedImpact parameter distributionof tracks associated toprimary verticesTrack segment26/03/13 Giovanni De Lellis, LNGS Seminar 39


Status of data analysis20122011RecordPerformancesabove quasi-online2010200920085844 located interactions4725 decay search26/03/13 Giovanni De Lellis, LNGS Seminar 2008-2009 completed2010 to 2012 ongoingwith optimized strategy 40


Charmed hadron production:an application of the decay searcha control sample for τ26/03/13 Giovanni De Lellis, LNGS Seminar 41


Charm sample:same topology but muon at interaction vertex26/03/13 Giovanni De Lellis, LNGS Seminar 42


Charm yield from the analysis of 2008÷2010 datacharm background expected data1 prong 20.5 ± 9.1 9 ± 3 29.5 ± 9.6 192 prong 14.9 ± 3.6 3.8 ± 1.1 18.7 ± 3.8 223 prong 4.6 ± 2.0 1.0 ± 0.3 5.6 ± 2.0 54 prong 0.8 ± 0.4 - 0.8 ± 0.4 4All 40.8±9.8 13.8±3.2 55±10 50Background, mostly from hadronic interactions(contribution from strange particle decay)26/03/13 Giovanni De Lellis, LNGS Seminar 43


Main characteristics of the charm candidate eventsMuon momentumImpact parameterKolmogorov test ≥ 0.99all plotsAngle in the transverseplane between µ and parentTrack multiplicity26/03/13 Giovanni De Lellis, LNGS Seminar 44


Physics results 26/03/13 Giovanni De Lellis, LNGS Seminar G. De Lellis - Fermilab - 4 June 201045


ν µ →ν e analysis4.1 GeV electron≈ 30 events found in the analyzed sample26/03/13 Giovanni De Lellis, LNGS Seminar 46


above. To illustrate the typical pattern of ν e candidates, figure 5 showsthe reconstructed image of a ν e candidate events, with the track segmentsobserved along the showering electron track.Electron neutrino search in 2008 and 2009 runs:134135136one of the ν e events with a π 0 as seen in the brickelectronγ showersInterfacefilms26/03/13 2 mm10 mm ECCCS19 candidates found in a sample of 505 neutrino interactions without muonFigure 5: Display of the reconstructed emulsion tracks of one of the ν e candidateevents. The reconstructed neutrino energy is 32.5 GeV. TwoGiovanni De Lellis, LNGS Seminar 47 tracks


Background from ν µ NC (π 0 →γγ) Gamma-­‐ray 1micronA close-up of an electron pairBG: 0.17 events (less than 1%)26/03/13 Giovanni De Lellis, LNGS Seminar 48


Energy distribution of the 19 ν e candidates Number of events / 10 GeV87654oscillated ν eby 3 flavor oscillationν ebeam contaminationBG from τ→ eBG from NC with π 0Dataoverflow32126026100 20 40 60 80 100 120 140 160Reconstructed energy (GeV)Energy cut 20 GeV 30 GeV No cutBG common to BG (a) from π 0 0.2 0.2 0.2both analyses BG (b) from τ → e 0.2 0.3 0.3Figure 6. Distribution of the reconstructed energy of the ν e 19.8±2.8 events, and (syst) theeventsexpected spectrufrom the differentν e beamsources contaminationin a stack histogram,4.2 7.7normalized 19.4to the number of pot analysed fothis paper. Binning for the experimental data energy distribution 3 flavour is done analysis according to the energresolution.Total expected BG in 3-flavour oscillation analysis 4.6 8.2 19.8BG to non-standard ν e via 3-flavour oscillation 1.0 1.3 1.4oscillation analysis onlyTotal expected BG in non-standard oscillation analysis 5.6 9.4 21.34 observed eventsAs the energy spectrum of the oscillated ν e with large 4.6 ∆m expected2 new (>0.1 eV 2 ) follows thspectrum of ν µ , which is basically vanishing above 40 GeV⇒ sin(see 2 (2θ13)


Searchintegerforfromnon-standardthe expectedoscillations background 9.4.at large Δm 2 values:exclusion plot in the sin 2 (2θ new ) - Δm 2 new plane)2(eV2newΔm21010Submitted to JHEP1arXiv:1303.3953LSND 90% C.L.LSND 99% C.L.KARMEN 90% C.L.NOMAD 90% C.L.BUGEY 90% C.L.CHOOZ 90% C.L.MiniBooNE 90% C.L.MiniBooNE 99% C.L.ICARUS 90% C.L. (F&C)OPERA 90% C.L. (Bayesian)-11010Caveat: experiments withdifferent L/E values-2-310-21026/03/13 Giovanni De Lellis, LNGS Seminar -110 2 1sin (2θ new)50


ν µ →ν τ analysis• 2008-2009 run analysis• Conservative approach: get confidence on thedetector performances before applying anykinematical cut• No kinematical cut• Slower analysis speed (signal/noise notoptimal)• Good data/MC agreement26/03/13 Giovanni De Lellis, LNGS Seminar 51


The first ν τ “appearance” candidate (2010) Candidate ν τ interac4on and τ decay from ν µ → ν τ oscilla4on 26/03/13 Giovanni De Lellis, LNGS Seminar 52


First tau neutrino candidate eventMuonless event 9234119599, taken on 22 nd August 2009(as seen by the electronic detectors)26/03/13 Giovanni De Lellis, LNGS Seminar 53 G. De Lellis - Fermilab - 4 June 2010


Event reconstruction in the brick26/03/13 τ − →ρ − ν τ ρ − →π 0 π - π 0 → γ γ Giovanni De Lellis, LNGS Seminar 54


PL17 PL18 PL19 PL20 PL21 1 5 7 3 careful visual inspec2on of the films behind/in front of the secondary vertex: Primary vertex 4 kink point 8 2 γ1 no “black” or “evapora2on” tracks. Support topological hypothesis of a par2cle decay 1mm lead 6 26/03/13Giovanni De Lellis, LNGS Seminar 55


Kinema2cal variables • Kinema2cal variables are computed by averaging the two independent sets of measurements • γ1 and γ2 both alached to 2 ry vertex VARIABLE AVERAGEkink (mrad) 41 ± 2decay length (µm) 1335 ± 35P daughter (GeV/c) 12 +6 -3Pt (MeV/c) 470 +240 -120missing Pt (MeV/c) 570 +320 -170ϕ (deg) 173 ± 226/03/13 Giovanni De Lellis, LNGS Seminar 56


Strategy for the 2010÷2012 runs • Apply kinematical selection• 15 GeV µ momentum cut (upper bound)• Anticipate the analysis of the most probable brickfor all the events before moving to the second(and further ones): optimal ratio betweenefficiency and analysis time• Anticipate the analysis of 0µ events (eventswithout any µ in the final state)• In view of 2012 Summer conferences: 1µ samplefor 2010 run, for 2011 run stick to 0µ sample only,2012 not yet analysed26/03/13 Giovanni De Lellis, LNGS Seminar 57


Second neutrino tau candidate event taken on 23 rd April 2011as seen by the electronic detector event display26/03/13 Giovanni De Lellis, LNGS Seminar 58


anima2on Second ν τ Candidate Event 2000 µm 26/03/13 Giovanni De Lellis, LNGS Seminar 59


Schematics of the event Φ Beam View Φ=167 o Secondary Interac2on In Emulsion 26/03/13 Giovanni De Lellis, LNGS Seminar 60 With four Nuclear fragments


Zoom of the primary interaction and decay region Decay point In Plas4c Base 26/03/13 Giovanni De Lellis, LNGS Seminar No Nuclear fragment Flight length 1.54mm 61


Momentum measurement and particleidentification of event tracks Track#Momentum(1σ interval)ParticleIDMethod / Comments[ GeV/c]Primary 2.8(2.1-3.5)d1 6.6(5.2 - 8.6)d2 1.3(1.1 -­‐1.5) Hadron • Momentum-RangeConsistency CheckStops after 2 brick walls.Incompatible with muon( 26÷44 brick walls)Hadron • Momentum-RangeConsistency CheckHadron • Momentum-RangeConsistency Checkd3 2.0(1.4 - 2.9)HadronInteraction in the Brick@ 1.3cm downstreamIndependent momentum measurements carried out in two labs 26/03/13 Giovanni De Lellis, LNGS Seminar 62


Kinematics of the second Candidate EventCutValueφ (Tau - Hadron) [degree] >90 167.8±1.1average kink angle [mrad] < 500 87.4±1.5Total momentum at 2ry vtx [GeV/c] > 3.0 8.4±1.7Min Invariant mass [GeV/c 2 ]Invariant mass [GeV/c 2 ]0.5


Kinematics of the second candidate eventcandidatecutSatisfying the criteria for à τ à3hadron decay26/03/13 Giovanni De Lellis, LNGS Seminar 64


After 2012 Summer conferences • Extension of the analysed sample to eventswith one µ in the final state26/03/13 Giovanni De Lellis, LNGS Seminar 65


Third tau neutrino event taken on May 2 nd 20122.8 GeV µ26/03/13 Giovanni De Lellis, LNGS Seminar 66


Analysis of the interface filmsµ trackSign of electromagnetic shower26/03/13 Giovanni De Lellis, LNGS Seminar 67


τ→µ candidatebrick analysis and decay search376 µm2 1ry trackτ candidate4 1 3 e-pairmuonplate 38 plate 39 plate 40 plate 41 plate 42Decay in the plastic base26/03/13 Giovanni De Lellis, LNGS Seminar 68


τ→µ candidateµm26/03/13 Giovanni De Lellis, LNGS Seminar 69


Third tau neutrino eventτ ൵m26/03/13 Giovanni De Lellis, LNGS Seminar 70


Third tau neutrino eventτ ൵m26/03/13 Giovanni De Lellis, LNGS Seminar 71


Event tracks’ featuresTRACK NUMBER PID MEASUREMENT 1 MEASUREMENT 2Θ X Θ Y P (GeV/c) Θ X Θ Y P (GeV/c)1DAUGHTERMUON -0.217 -0.0693.1[2.6,4.0]MCS-0.223 -0.0692.8±0.2Range (TT+RPC)2HADRONRange0.203 -0.1253 PHOTON 0.024 -0.1554PARENT0.85[0.70,1.10]2.64[1.9,4.3]0.205 -0.1150.029 -0.1600.96[0.76,1.22]3.24[2.52,4.55]TAU -0.040 0.098 -0.035 0.096γ attachment 26/03/13 Giovanni De Lellis, LNGS Seminar 72


Muon charge and momentum reconstructionBending by themagnetic fieldMuon momentumby range in the electronic detector: 2.8±0.2 GeV/cMCS in the brick consistent 3.1 [2.6,4.0] GeV/cϑ (mrad)Cells26/03/13 Giovanni De Lellis, LNGS Seminar 73


Charge determination of the muonCharge measurement based on TT and RPC hits when no hits in drift tubesFit function:X(z) = p0 + p1 x (z-z0) + p2 x (z-z0) 2 for z>z0, start of magnetized regionX(z) = p0 + p1 x (z-z0)for z


Track follow down to assess the nature of track 2Track 2 interacting in thedownstream brick withoutvisible charged particlesMomentum/range inconsistent with µ hypothesis0.9 GeV/4 cm LeadD =LR lead( p)ρ leadρ averageL = track lengthR lead = µ rangeρ average = average densityρ lead = lead densityp = momentum in emulsiontrack value Hadrons and muon stopping in the brick cut value D variable26/03/13 Giovanni De Lellis, LNGS Seminar 75


Kinematical variables VARIABLE AVERAGEKink angle (mrad) 245 ± 5decay length (µm) 376 ± 10τ→μ MCτ→μ candidatePµ (GeV/c) 2.8±0.2Pt (MeV/c) 690±50ϕ (degrees) 154.5 ± 1.526/03/13 Giovanni De Lellis, LNGS Seminar 76


Kinematical variables. All cuts passed: τ ൠcandidateτ→μ MCτ→μ candidateexcluded region26/03/13 Giovanni De Lellis, LNGS Seminar 77


Background studies26/03/13 Giovanni De Lellis, LNGS Seminar 78


Improvements on the background rejection: large angle track detectionUndetected soft and large angle muons are the source of charm backgroundDetection of particles and nuclear fragments in hadronic interactionsTracking efficiencyε 72 degrees! tg(theta) 90% 80% Two different approachesget comparable results|tanθ|=1.0 |tanθ|=2.0 |tanθ|=3.0 26/03/13 Giovanni De Lellis, LNGS Seminar 79


Nuclear fragments are a clearhadron interaction To reduce and quantify the hainteraction kink B.G.increase sensitivityBackground studies: hadronic interactionsComparison of large data sample (π - beam test at CERN) with Fluka simulation:check the agreement and estimate the systematic error of simulationTrack length analysed in the brick: 2 GeV/c : 8.5 m, 4 GeV/c : 12.6 m, 10 GeV/c : 38.5 mInteraction ratehadronBackward fragment trackBlack : π - beam dataRed : MC (FLUKA) simulation 26/03/13 Giovanni De Lellis, LNGS Seminar 80


2GeV/c Multiplicity 10 GeV/cSecondary track emission4GeV/c 10GeV/c Kink angle (1-prong) Error bars : Experimental dataHistogram : Simulated data Good agreement within the statistical error: systematic error reduced to 30% 26/03/13 Giovanni De Lellis, LNGS Seminar 81


ν NC h Nuclear fragments emission probability NuclearFragmentsh Highly ionizing fragmentsBlack : experimental dataRed : simulated data (β = p/E = 0.7)It provides additional background reduction.26/03/13 Giovanni De Lellis, LNGS Seminar 82


Nuclear fragments in 1 and 3 prong interactions Multiplicity 2GeV/c 4GeV/c 10GeV/c MC: β < 0.7 Emission angle(cos θ) Error bars : experimentHistogram : simulation Backward Forward Backward Forward Backward Forward Agreement within the statistical error: systematic error is 10%. 26/03/13 Giovanni De Lellis, LNGS Seminar 83


Large angle muon scatteringKink angle (mrad)Pt (MeV/c)Kink angle (>20 mrad)Pt (> 250 MeV/c)Rate in lead (10 -6 ) and less in emulsion/base (10 -8 to 10 -7 ). No measurements exceptan upper limit: S.A. Akimenko et al., NIM A423 (1986) 518 (< 10 -5 in lead). 10 -5 rate usedPlan to revise this number by an experimental measurement with emulsion26/03/13 Giovanni De Lellis, LNGS Seminar 84


Statistical considerationsSample analysed for Summer 2012 conferencesSummer conferencesSignal Background Charm µ scattering had intτà h 0.66 0.045 0.029 0.016τ à 3h 0.61 0.090 0.087 0.003τ à µ 0.34 0.017 0.005 0.012τ à e 0.49 0.065 0.065total 2.10 0.217 0.186 0.012 0.0192 observed events in the τà h and τà 3h channelsPvalue = P 0 = 3.819 x 10 -3Probability to be explained by background = 0.0134This corresponds to 2.2 σ significance of non-null observation26/03/13 Giovanni De Lellis, LNGS Seminar 85


Statistical considerationsExtended sample to muonic interactionsExtended sampleSignal Background Charm µ scattering had intτà h 0.66 0.045 0.029 0.016τ à 3h 0.61 0.090 0.087 0.003τ à µ 0.56 0.026 0.0084 0.018τ à e 0.49 0.065 0.065total 2.32 0.226 0.19 0.018 0.0193 observed events in the τà h and τà 3h and τൠchannelsPvalue = P 0 = 1.125 x 10 -4Probability to be explained by background = 7.29 10 -4This corresponds to 3.2 σ significance of non-null observation26/03/13 Giovanni De Lellis, LNGS Seminar 86


Exploit kinematical characteristicsof the events: likelihood analysisData/MC agreement for relevantvariables26/03/13 Giovanni De Lellis, LNGS Seminar 87


7Momentum measurement by multiple Coulomb scattering foridentified µ in the 2÷6 GeV 17 range(GeV/c)P MCS8765N events18 (http://iopscience.iop.org/1367-2630/1(left) and for a muon track with an incidentcoordinate (right). The dashed line shows thFigure 2. Representation of the number of possibleσ measurements = (22 ± 4)% available16obtained with the momentum measured by thwhen applying the MCS method up to N cell = 3.14View thesolidtablelineofcorrespondscontentsto thefor momentumthis issumeaemulsion.12Momentum measurement by th3D coordinates0.01emulsion targetPED0.003track angle = 98 mrad0.0This article has been downloaded fro0 2 4 6 8 10 12 142012 New J. Phys. 14 013026the MCS algorithm, charged current interactions where a410 electronic detectors with a momentum below 6 GeV c 1 w38neutrino interaction vertices were located in the emulsion taevent was matched to the muon track predicted by the electron6 criteria have been applied on track quality and length. The re2cells. The final sample corresponds to 43 events. Figure 13 sho4 deviation on the thickness of lead traversed in the 3D (left) and12different Download muon tracks. details: The dashed line shows the expected anthe momentum measured by the electronic detectors, while the00 the IP momentum Address: by the151.70.67.100MCS method described in this paper. Th0 1 2 3 4 5 6 7 8 -2 -1.5from-1MCS -0.5and0electronic detectors1 1.5are2fully compatible.P ED(GeV/c)TheThearticle muon momentawasindownloaded theon 17/01∆selected p/p sample range from 226/03/13 Giovanni De Lellis, LNGS Seminar the left plot of figure 14, which shows the correlation 88 betweenplot shows the relative difference with respect to the electronic(rad)θ measured0.0090.0080.0070.0060.0050.004= 2.93 GeV/cP = 3.04 GeV/cMCS2χ / ndf2.107 / 13Prob 0.9997p0 3035 ±187N cell(rad)θ measuredTransvFigure 13. The angular deviation dependence oby a muon track with an incident angle of 980.000.00.00.0


Track emission angles, momentum, Φ angleTrack momentumAngle difference with µin the transverse plane26/03/13 Giovanni De Lellis, LNGS Seminar 89


Statistical analysis26/03/13 Giovanni De Lellis, LNGS Seminar 90


Angle between the parent particle and the hadron jet in the transverse planediscard the largest φ track unless it is identified as hadrondegrees26/03/13 Giovanni De Lellis, LNGS Seminar 91


Decay position (micron)26/03/13 Giovanni De Lellis, LNGS Seminar 92


Transverse momentum at secondary vertex(GeV/c)26/03/13 Giovanni De Lellis, LNGS Seminar 93


LL analysis of first event: e.g. charm1.00 12.8% have beler LL than 1 st event π/2 Φπ 0 Pt 1.5 Pt at decay (GeV/c)z 0 3890 μm Decay position26/03/13 Giovanni De Lellis, LNGS Seminar 94


LL analysis of second event: e.g. hadron scattering -­‐1.68 49.7% have beler LL than 2 nd event π/2 Φπ 0 Pt at decay (GeV/c) 1.5 0 Decay position 3890 μm 26/03/13 Giovanni De Lellis, LNGS Seminar 95


LL analysis of third event: e.g. µ scattering 1.53 4.65% have beler LL than 3 rd event π/2 Φπ 0 Pt at decay (GeV/c) 1.5 0 Decay position 3890 μm 26/03/13 Giovanni De Lellis, LNGS Seminar 96


Statistical considerationssample analysed for 2012 Summer conferencesCombining different channels: Likelihood based method, see e.g. G. Cowan et al.,Eur. Phys. J. C71 (2011) 15542.3 σ significanceSummer 2012 conferencesSignal Background Charm µ scattering had intτà h 0.66 0.045 0.029 0.016τ à 3h 0.61 0.090 0.087 0.003τ à µ 0.34 0.017 0.005 0.012τ à e 0.49 0.065 0.065total 2.10 0.217 0.186 0.012 0.01926/03/13 Giovanni De Lellis, LNGS Seminar 97


Statistical considerationsExtended sample to muonic interactions3.5 σ significanceExtended sampleSignal Background Charm µ scattering had intτà h 0.66 0.045 0.029 0.016τ à 3h 0.61 0.090 0.087 0.003τ à µ 0.56 0.026 0.0084 0.018τ à e 0.49 0.065 0.065total 2.32 0.226 0.19 0.018 0.0193.6 σ significance3.8 σ significance withindependent analysis26/03/13 Giovanni De Lellis, LNGS Seminar 98


Evidence for ν µ à ν τ in appearancemode• Three events reported in an extended sample• Conservative background evaluation• Significance of 3.2σ with simple countingmethod• With a first likelihood approach, 3.5σ level• 4σ observation within reach in 201326/03/13 Giovanni De Lellis, LNGS Seminar 99


Thank you for your alen2on 26/03/13 Giovanni De Lellis, LNGS Seminar 100

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