Study of Direct Photon plus Jet production in CMS Experiment at \sqrt{s}=14 TeV

TL;DR

This paper presents simulation-based analysis of direct photon plus jet production at 14 TeV in CMS, optimizing cuts to improve signal-to-background ratio for better understanding of QCD and background processes.

Contribution

It introduces optimized isolation and angular cuts in CMS simulations, significantly enhancing the signal-to-background ratio for gamma+jet events at 14 TeV.

Findings

Isolation cuts improve S/B by ~25%

Large Δφ cut increases S/B by ~15%

Overall S/B ratio improves by ~42%

Abstract

We present simulation results of $\gamma$ + Jet analysis using CMS (Compact Muon Solenoid) Object-Oriented software at the Large Hadron Collider (LHC) center of mass energy $\sqrt{s}$=14 TeV. The study of direct photon production helps in validating the perturbative Quantum Chromodynamics (pQCD) and providing information on the gluon distribution in the nucleons. Direct photon processes also constitute a major background to several other Standard Model (SM) processes and signals of new physics. Thus these processes need to be understood precisely in the new energy regime. In this work, we have done a detailed study of the GEANT4 simulated $\gamma$ + jet events generated with Pythia, and the related background processes. Isolation cuts have been optimized for direct photon which improves the signal over background ratio by $\sim25%$ as compared to previous studies done in CMS. The inclusion of a large $\Delta\phi$ cut between the photon and the leading jet at $40^0$ in the analysis leads to a further increase of $\sim15%$ in S/B, thus giving an overall gain of $\sim42%$ in S/B ratio.