On the application of 'photon+jet' events for setting the absolute jet energy scale and determining the gluon distribution at the LHC

Abstract

We study the impact of new set of cuts, proposed in our previous works, on the improvement of accuracy of the jet energy calibration with &#39;p p ->photon+Jet+X&#39; process at LHC. Monte Carlo events produced by the PYTHIA 5.7 generator are used for this aim. The selection criteria for &#39;photon+jet&#39; event samples that would provide a good balance of photon Pt with jet Pt and would allow to reduce the background are described. The distributions of these events over photon Pt and jet pseudorapidity are presented. The features of &#39;photon+jet&#39; events in the barrel region of the CMS detector (|eta^{jet}| < 1.4) are exposed. The efficiency of the cuts used for background suppression is demonstrated. It is shown that the samples of &#39;photon+jet&#39; events, gained with the cuts for the jet energy calibration, may have enough statistics for determining the gluon distribution inside a proton in the region of x > 2*10^{-4} and of Q^2 by two orders higher than that studied at HERA.