Abstract
In proton-proton collisions at the LHC, pairs of top and anti-top quarks are expected to be mostly produced through gluon fusion, in contrast to production at the Tevatron, where quark annihilation dominates. Making use of the large number of top quark pairs, we present measurements of the spin correlation between top and anti-top quarks as well as of the top quark charge asymmetry, which constitute important tests of QCD and are sensitive to new physics. We also discuss top production in association of photons and Z bosons.
Highlights
At the LHC the top quark is produced mostly in pairs
The decay modes of the two W bosons define three possible signatures: the all hadronic channel, when both Ws decay into a quark and an anti-quark, is characterized by four lightquark jets and two b-jets; the dilepton channel, when both Ws decay into a charged lepton and a neutrino, is characterized by two opposite sign leptons, two b-jets and large missing transverse momentum; and the semileptonic channel with one hadronic and one leptonic W-boson decay, is characterized by one lepton, two jets, two b-jets and missing transverse momentum
The measurements described here are performed in dilepton and semileptonic channels using, partially or in full, the data set√collected at the ATLAS experiment [1] during the 2011 s = 7 TeV run
Summary
At the LHC the top quark is produced mostly in pairs. Given its short lifetime (≈ 5 × 10−25 s), each top quark decays rapidly into a W boson and a b quark, before hadronization can occur. Top pair properties are directly accessible through its decay products. The decay modes of the two W bosons define three possible signatures: the all hadronic channel, when both Ws decay into a quark and an anti-quark, is characterized by four lightquark jets and two b-jets; the dilepton channel, when both Ws decay into a charged lepton and a neutrino, is characterized by two opposite sign leptons, two b-jets and large missing transverse momentum; and the semileptonic channel with one hadronic and one leptonic W-boson decay, is characterized by one lepton, two jets, two b-jets and missing transverse momentum.
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