Measurement of the b-jet production cross section using muons in jets with ATLAS in pp Collisions at $/sqrt{s}=7$ TeV

We present a measurement of the inclusive $b$-jet production differential cross section in proton-proton collisions at $sqrt{s}$ = 7 TeV, using a sample of jets containing a muon. The sample was collected using the ATLAS detector during 2010 and corresponds to an integrated luminosity of 38~pb$^{-1}$. The event selection requires the muon to have a transverse momentum $p_T^mu>4$ GeV and the jet to have $p_T>30$ GeV and rapidity $|y|<2.1$. The transverse momentum of the muon with respect to the $b$-jet axis, ptrel, is used to determine the $b$-purity of the sample, which include jets with a $b$-hadron decaying semileptonically, and a background of charm and light jets. A dedicated algorithm is employed to estimate the $b$-jet transverse momentum $p_T^b$ from the reconstructed jet and muon momenta, recovering also the momentum carried by the neutrino in the semileptonic $b$-decay. The inclusive $b$-jet differential cross section, ${dsigma}/{d p_T^{b-jet}}$ is compared to next-to-leading order QCD predictions from the Powheg generator, as well as to an independent ATLAS $b$-jet cross section measurement using inclusive jets tagged with a displaced secondary vertex.