Measurement of multi-jet production cross sections, the strong coupling constant alphas and jet properties with the ATLAS detector

The production of multi­jet final states at hadron colliders probes pQCD at several mass scales. The processes can also be used to probe the gluon density function of the proton. The ATLAS collaboration has measured the production of 4­jets final states in in 20.3 /fb of data collected at a center­of­mass energy of 8 TeV. The measurements have been performed differentially as a function of a variety of kinematic and topological observables, amongst others the rapidity separation between the leading two jets. The results are compared with state­of­the­art theory calculations at NLO in pQCD, with the predictions of several MC generators as well as resummation calculations by in the HEJ approximation. The collaboration has also used multi­jets events in data taken at an effective integrated luminosity of 158 /pb at a center­of­mass energy of 7 TeV to measure the transverse energy correlation and its asymmetry and derive a measurement of the strong coupling constant. The average charge and the multiplicity of charged hadrons within a jet provide new insights into the modeling of strong interactions. The jet charge is sensitive to the electric charge of the parton initiating a jet and the number of charged particles within a jet provides a powerful means to distinguish gluon­initiated from quark­initiated jets. These quantities were measured by the ATLAS collaboration using a selection of di­jet events in 20.3 /fb of data collected at a center­of­mass energy of 8 TeV. The results have been compared with pQCD predictions and with predictions of MC generators.