Measurement of the production cross section for Z/gamma* in association with jets in pp collisions at sqrt(s) = 7 TeV with the ATLAS Detector

The study of the production of jets of particles in association with a Z/gamma* boson in proton-proton collisions at sqrt(s) = 7 TeV provides a stringent test of perturbative quantum chromodynamics (pQCD). The proper understanding of events containing QCD jets in association with a Z/gamma* boson in the Standard Model (SM) is a fundamental element of the LHC physics program of searches for new physics, for which events with such final states constitute irreducible backgrounds. These SM background contributions are estimated using Monte Carlo (MC) predictions that include leading-order (LO) matrix elements supplemented by parton showers, which a priori are affected by large scale uncertainties and need to be tuned and validated using data. We present measurements of inclusive jet cross sections in Z/gamma* events, with Z/gamma* decaying into electron or muon pairs, as a function of jet transverse momentum and jet multiplicity, using 33 pb−1 of data collected by the ATLAS experiment in 2010. The measurements are compared to next-to-leading-order pQCD calculations, and to predictions from different MC generators implementing LO matrix elements supplemented by parton showers.