Measurement of the top quark pair production cross section with ATLAS in pp collisions at √s = 7 TeV in dilepton final states

• A measurement is presented of the production cross section of top quark pairs (σ_{\ttbar{}}) in proton-proton (pp) collisions at √s = 7 TeV recorded with the ATLAS detector at the CERN Large Hadron Collider. Using a data sample of 35 pb−1, candidate events are selected in the dilepton topology with large missing transverse energy, \met{}, and at least two jets.A baseline analysis employing kinematic properties of the candidate events to separate the signal from background and using data-driven techniques to determine the most important backgrounds, results in a measurement ofσ_{\ttbar{}} = 173 ± 22(stat.)+18 −16(syst.)+8 −7(lum.) pb,where the three uncertainties are from statistics, systematics and integrated luminosity, respectively.We also perform a cross section measurement requiring at least one b-tagged jet and a looser kinematic selection that increases the signal-to-background ratio, yieldingσ_{\ttbar{}} = 171 ± 22(stat.)+21 -16(syst.)+7 −6(lum.) pb.Additional studies are performed to corroborate these measurements; a technique that normalizes the \ttbar{} signal yield to the measured rate of Z decays, a two-dimensional template shape fit using the \met{} vs the number of jets to simultaneously measure the production cross sections of \ttbar{}, WW and Z → ττ final states, and a simultaneous measurement of σ_{\ttbar{}} and the b-tagging efficiency using the distribution of the number of tagged jets in each event.All the measurements are in good agreement with each other and the Standard Model prediction.

Subject headings

NATURVETENSKAP  -- Fysik -- Subatomär fysik (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences -- Subatomic Physics (hsv//eng)

Keyword

fysik

Physics

Publication and Content Type

vet (subject category)

rap (subject category)