Measurement of the cross-section for $W$ boson production in association with $b$-jets in $pp$ collisions at $\sqrt{s} = 7$ \TeV\ with the ATLAS detector

This note reports a measurement of the W+b-jets cross-section in proton-proton collisions at a centre-of-mass energy of 7 TeV at the LHC. These results are based on data corresponding to an integrated luminosity of 4.6 fb-1, collected with the ATLAS detector. Cross-sections are presented as a function of jet multiplicity and of the transverse momentum of the leading b-jet for both the muon and electron decay modes of the W boson. The W+b-jets cross-section, corrected for all known detector effects, is quoted in a limited kinematic range, using jets reconstructed with the anti-k_t clustering algorithm with transverse momentum above 25 GeV and rapidity within $\pm$ 2.1. Combining the results from the muon and electron channels, the fiducial cross-section for W+b-jets is measured to be 7.1 $\pm$ 0.5 (stat) $\pm$ 1.4 (syst) pb.