2011 QCD and High Energy Interactions - Rencontres de Moriond ...

SM
σ
/
σ
95% CL Limit on
3
10
2
10
10
1
­1
10
ATLAS Preliminary
Observed PCL
Expected PCL
± 1σ
+ 2σ
­1
Tevatron = 5.9 fb
Observed CLs
Expected CLs
­1
Ldt = 35 pb
s = 7 TeV
Observed CLs
Expected CLs
Tevatron
Exclusion
120 130 140 150 160 170 180 190 200
∫
mH
[GeV]
) (pb)
ν
2l2
→
WW
→
BR(H
⋅
σ
20
18
16
14
12
10
8
6
4
2
CMS,
­1
s = 7 TeV, L = 36 pb
int
σH
⋅ BR(H → WW → 2l2ν),
SM
σH
⋅ BR(H → WW → 2l2ν),
SM4
upper limit, observed
upper limit, expected ± 1σ
upper limit, expected ± 2σ
0
100 200 300 400 500 600
2
Higgs boson mass [GeV/c ]
Figure 1: 95% CL limits on the Higgs boson production cross-section set by the ATLAS (left) and CMS (right)
H → WW → ℓνℓν searches.
SM
σ
/
σ
95% C.L. limit on
160
140
120
100
80
60
40
20
ATLAS Preliminary
Observed (PCL)
Expected (PCL)
H→ZZ→llνν
± 1σ
+ 2 σ
­1
Ldt=35pb , s=7TeV
∫
0
200 250 300 350 400 450 500 550 600
mH
[GeV]
SM
σ
/
σ
95% C.L. limit on
160
140
120
100
80
60
40
20
ATLAS Preliminary
Observed (PCL)
Expected (PCL)
H→ZZ→llνν/llqq
± 1σ
+ 2 σ
­1
Ldt=35pb , s=7TeV
∫
0
200 250 300 350 400 450 500 550 600
mH
[GeV]
Figure 2: Left: 95% CL limits on the Higgs boson production cross-section set by the ATLAS H → ZZ → ℓνℓν
search. Right: the limit obtained by combining the H → ZZ → ℓνℓν and H → ZZ → ℓνqq searches.
to study even in 35 pb −1 of data 11 , although the backgrounds in these channels are higher as
well. A search for the former decay mode proceeds by selecting events with two leptons and
large Emiss T and reconstructing the transverse mass of the ℓℓνν system, while in a search for
the ℓℓqq final state one can fully reconstruct the invariant mass of the ZZ system. Figure 2
shows the upper bounds on the Higgs boson production cross-section (in units of the Standard
Model prediction) obtained from H → ZZ → ℓℓνν alone (left) and from the combination of the
ℓℓνν and ℓℓqq channels (right). In the combined limit, the upper bound on the Higgs boson
production cross-section ranges from 3.5 times the Standard Model prediction at low mass to
about 30 times the Standard Model prediction at high mass.
3 H → γγ, H/A → ττ, and Charged Higgs
For Higgs bosons with a mass below about 140 GeV, the H → γγ decay mode offers one of
the most important discovery modes. A Higgs boson decaying to this final state would give rise
to a narrow peak in the γγ invariant mass spectrum, with a FWHM of 4.4 GeV at ATLAS 12 .
Figure 3 (left) shows the upper limit from ATLAS on the H → γγ production cross-section in
units of the Standard Model prediction. The upper limit varies between 8 and 38 times the