Measurement of the WW cross section in s = 7 TeV pp collisions with the ATLAS detector and limits on

The MIT Faculty has made this article openly available. Please share how this access benefits you. Your story matters. Measurement of the W W cross section in √ s = 7 TeV pp collisions with the ATLAS detector and limits on anomalous gauge couplings ✩ .ATLAS Collaboration a r t i c l e i n f o a b s t r a c t This Letter reports a measurement of the W W production cross section in √ s = 7 TeV pp collisions using data corresponding to an integrated luminosity of 1.02 fb −1 collected with the ATLAS detector. Using leptonic decays of oppositely charged W bosons, the total measured cross section is σ (pp → W W) = 54.4 ± 4.0 (stat.) ± 3.9 (syst.) ± 2.0 (lumi.) pb, consistent with the Standard Model prediction of σ (pp → W W) = 44.4 ± 2.8 pb. Limits on anomalous electroweak triple-gauge couplings are extracted from a fit to the transverse-momentum distribution of the leading charged lepton in the event. Measurements of W W production at the LHC provide important tests of the Standard Model (SM), in particular of the W W Z and W W γ triple gauge couplings (TGCs) resulting from the non-Abelian nature of the SU(2) L × U (1) Y symmetry group. Precise measurements of TGCs are sensitive probes of new physics in the electroweak sector and are complementary to direct searches. Furthermore , since W W production is a background to possible new processes such as the production of the SM Higgs boson, a precise measurement of the W W cross section is an important step in the search for new physics. This Letter describes the measurements of the W W cross section and of TGCs in pp collisions at √ s = 7 TeV. The dominant SM W W production mechanisms are s-channel and t-channel quark– antiquark annihilation, with a 3% contribution from gluon–gluon fusion. The cross section is measured in the fiducial phase space of the detector using W W → lνlν decays in final states with electrons and muons, and is extrapolated to the total phase space. The fiducial phase space includes geometric and kinematic acceptance. The total production cross section of oppositely charged W bosons is measured according to the equation [1] σ (pp → W W) = (1) where N data and N bg are the number …