Separation of quark and gluon jets in the direct photon production processes at the LHC using the neural network approach

A neural network technique is used to discriminate between quark and gluon jets produced in the qg->q+photon and q q->g+photon processes at the LHC. Considering the network as a trigger and using the PYTHIA event generator and the full event fast simulation package for the CMS detector CMSJET we obtain signal-to-background ratios.Comment: 22 pages, uses cernrep.cls style fil

Jet energy scale setting with "Gamma+Jet" events at LHC energies. Detailed study of the background suppression

The possibilities of the background events suppression, based on the QCD subprocesses of qg-, gg-, qq- scattering with big cross sections, to the signal \gpj events are studied. Basing on the introduced selection criteria, the background suppression factors and signal events selection efficiencies and the number of the events, that can be collected at LHC with low luminosity L=10^{33}cm^2 s^{-1} during one month of continuous work, are determined.Comment: 23 pages, 9 figures, uses cernrep.cls style fil

Jet energy scale setting with "photon+Jet" events at LHC energies. Selection of events with a clean "photon+Jet" topology and photon Pt - jet Pt disbalance

It is shown in the paper that Pt activity limitation (modulus of the vector sum) of all particle beyond "photon+Jet" system Pt^out leads to the noticeable photon Pt - jet Pt disbalance decreasing. On a simultaneous restriction of the cluster Pt and Pt^out from above it is possible to reach an acceptable balance between photon Pt - jet Pt with a sufficient number of the photon Pt - jet Pt events for the jet energy scale setting and hadron calorimeter calibratiom of the CMS detector at LHC.Comment: 7 pages, 7 figures, uses cernrep.cls style fil

Jet energy scale setting with "photon+Jet" events at LHC energies. Minijets and cluster suppression and photon Pt - jet Pt disbalance

In this paper the study of "photon+Jet" events is continued and the event number determination useful for jet energy scale setting with the possible CMS detector hadron calorimeter calibration at LHC is fulfiled. The sources of photon Pt and jet Pt disbalance are exposed. It is shown that the cluster Pt limitation, which is found in an event outside of the jet, can be a good criterion for this disbalance decreasing.Comment: 19 pages, uses cernrep.cls (modified

"photon+Jet" events rate estimation for gluon distribution determination at LHC

It is shown that "photon+Jet" events, being collected at LHC, would provide us with the data sufficient for an extraction of gluon distribution function in a proton using valence and s quark distributions measured in the same experiment with another physical proces A new region of 10^{-4}< x < 10^{-1} with 1.6x10^3 photon +Jet events are also given.Comment: 9 pages, 1 figure, modified cernrep.cls fil

On the possibility of discrimination between π0,η,ω,Ks0\pi^0, \eta, \omega, K^0_s mesons and a photon based on the calorimeter information in the CMS detector

The possibility of separating the $\pi^0, \eta, \omega$ and $K^0_s$ meson background from the signal photons produced directly in $pp$ collisions is analyzed. The rejection factors for two pseudorapidity regions 0.4<\eta<1.0$and 1.6<\eta<2.0$ and six Et values, 20, 40, 60, 80, 100 and 200 GeV, are calculated for a case when only the calorimeter information is used. The cases of $\eta, \omega$ and $K^0_s$ mesons decaying through the neutral and charged channels are considered separately.Comment: 17 pages, uses cernrep.cls style fil