Measurement of the production cross-section of a W boson in association with a charm quark in pp collisions at √(s) = 8 TeV in ATLAS

The production cross-section of a W boson in association with a single charm quark at hadron colliders is sensitive to the strange quark parton distribution function (PDF). W+c production is dominated by strange-gluon scattering, for which the final state W boson is accompanied by a charm quark of opposite charge. The W boson is selected through its leptonic decay, while the charm quark is selected through the semi-leptonic decay of the charmed hadron into a soft muon. The signal is selected by requiring the charge of the W boson decay lepton and the muon from the charmed hadron decay to have opposite sign, while the backgrounds are mostly symmetrical between same sign and opposite sign channels. Preliminary results on the measurement of the production cross-section for the 2012 data at √(s) = 8 TeV using 20.3 fb^-1 of pp collisions are presented. The estimation of the residual backgrounds using data-driven methods are discussed in detail, with particular attention given to the multijet and W+light-jet backgrounds. A discussion of the systematic uncertainties is included in the presentation.