Search for new particles decaying to dijet in 7 tev proton-proton collisions at CMS

This thesis presents a measurement of the dijet invariant mass spectrum and searchfor new particles decaying to dijets at CMS in 7 TeV pp collisions using data correspondingto an integrated luminosity of 2.875 pb?1. The measured dijet mass distribution iscompared to QCD prediction from PYTHIA . It is required the pseudorapidity separationof the two jets to satisfy |Delta eta| < 1.3 with each jet inside the region of |eta| < 2.5. Theobserved dijet mass spectrum is fitted by a smooth function to search for dijet resonances.Since there is no evidence for dijet resonances, the upper limits at 95% Confidence Level(C.L.) on the resonance cross section are set. These generic cross section limits are comparedwith theoretical predictions for the cross section for several models of new particles:string resonances, axigluons, colorons, excited quarks, E6 diquarks, Randall-Sundrumgravitons,W' and Z'.It is excluded at 95% C.L. string resonances in the mass range 0.50 < M(S) <2.50 TeV, excited quarks in the mass range 0.50 < M(q*) < 1.58 TeV, axigluons andcolorons in the mass ranges 0.50 < M(A) < 1.17 TeV and 1.47 < M(A) < 1.52 TeV,and E6 diquarks in the mass ranges 0.50 < M(D) < 0.58 TeV, 0.97 < M(D) < 1.08 TeV,and 1.45 < M(D) < 1.60 TeV. These exclusions extend previously published limits on allmodels.