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

2
Events/2GeV/c
50
40
30
20
10
CMS Preliminary
s = 7 TeV, L = 36 pb
-1
Data
tt
Z+b
Z+c
Z+l
High Efficiency
b-tagging
0
60 70 80 90 100 110 120
2
M + - (GeV/c )
l l
)
2
Events / ( 0.167 GeV/c
35
30
25
20
15
10
5
CMS Preliminary
-1
s = 7 TeV, L = 36 pb
Data
b-jets
c-jets
l-jets
High efficiency b-tagging
0
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
2
Secondary vertex mass (GeV/c )
Figure 4: Di-lepton mass (left) and secondary vertex mass (right) of events passing the HE selection compared
to the simulation.
the HE selection. Results are summarised in Table 1 for the high-efficiency and high-purity
selections. Values expected from simulation and theory are also given.
Table 1: Ratio R = σ(pp→Z+b+X)
from data and from MadGraph samples, and expected value from NLO theory.
σ(pp→Z+j+X)
Sample R(Z → ee) (%), p e T > 25 GeV, |η e | < 2.5 R(Z → µµ) (%), p µ
T > 20 GeV, |ηµ | < 2.1
Data HE 4.3 ± 0.6(stat) ± 1.1(syst) 5.1 ± 0.6(stat) ± 1.3(syst)
Data HP 5.4 ± 1.0(stat) ± 1.2(syst) 4.6 ± 0.8(stat) ± 1.1(syst)
MadGraph 5.1 ± 0.2(stat) ± 0.2(syst) ± 0.6(theory) 5.3 ± 0.1(stat) ± 0.2(syst) ± 0.6(theory)
MCFM 10
4.3 ± 0.5(theory) 4.7 ± 0.5(theory)
5 Conclusions
Several studies of the production of jets in association with W and Z bosons in pp collisions
at a centre-of-mass energy of 7 TeV using 36 pb −1 of collected data have been presented. All
measurements, including the jet rates, the polarization of W and the production of b-quarks
with Z bosons, are in agreement with Standard Model expectations. The precision reached in
these analyses involving lepton, jet and MET reconstruction, and b-tagging, clearly establishes
the readiness of the CMS experiment for searches beyond the Standard Model.
References
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