Abstract
A summary of recent results from the ATLAS experiment at the LHC in the field of W ± Z and diboson physics is presented. Inclusive W ± and Z production cross sections were measured differentially and compared to different PDF sets. The ratio of the total W ± and Z cross section was used to measure the strange quark density in the light quark sea. The first measurement of tau polarisation made at a hadron collider is presented. Cross section measurements for the diboson processes W ± γ, Zγ, W + W − , W ± Z and ZZ are presented. The diboson measurements are used to set limits on anomalous Triple Gauge Couplings; the results are consistent with the Standard Model values.
Highlights
W± and Z bosons are produced at a high rate at the LHC, and during LHC running in 2010 and 2011 the ATLAS experiment [1] has collected large statistics data samples of W± and Z events
Measurements of W± and Z production give an important test of Quantum Chromodynamics (QCD)
Precise measurements of the cross sections give the ability to distinguish between predictions obtained using different PDF sets
Summary
W± and Z bosons are produced at a high rate at the LHC, and during LHC running in 2010 and 2011 the ATLAS experiment [1] has collected large statistics data samples of W± and Z events. Since the production of W± and Z bosons is independent of the decay lepton flavour, the ratio of the electron to the muon channel cross sections in W± or Z decays gives a measurement of the ratios of the branching fractions. The angle θ between the τ direction of flight and the hadronic decay products in the τ rest frame is the primary observable sensitive to the polarisation. This is not directly accessible experimentally as the τ momentum reconstruction is limited due to the multiple unobserved neutrinos in the event. This is compatible with the Standard Model expectation of - 1, and is the first measurement of the τ polarisation at a hadron collider
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