Measurement of the Z/gamma* + bb-jets cross section in pp collisions at sqrt(s) = 7 TeV

The production of a Z boson, decaying into two leptons, and produced in association with one or more b jets, is studied using proton-proton collisions delivered by the LHC at a centre-of-mass energy of 7 TeV and recorded by the CMS detector, with a data sample collected in 2011 corresponding to an integrated luminosity of 5$\,$fb$^{-1}$. Cross sections of the Z$(\ell\ell)$+b-jet(s) processes (where $\ell\ell$ = ee or $\mu\mu$) are measured for Z bosons produced in association with exactly one or at least two b jets, as well as the cross section ratio of a Z boson produced in association with any number of b jets relative to those containing any number of jets. The cross sections are estimated at the particle level for events containing leptons with $p_{\textrm{T}}^{\ell}>20$ GeV and $|\eta^\ell|<2.4$, a dilepton invariant mass $76<M_{\ell\ell}<106$ GeV, jets with $p_{\textrm{T}}^{j}>25$ GeV and $|\eta^j|<2.1$, and a seperation between the leptons and the jets of $\Delta R(l,j)>0.5$. The estimated cross sections are then compared with different theoretical predictions. Also, kinematic properties are compared with the predictions from the MadGraph event generator, interfaced with Pythia for the parton shower.