Commissioning of EndCap RPCs and the Study of c States with CMS Detector at p s = 7 TeV

Abstract

Resistive plate chambers (RPC) are fast gaseous detectors that provide a dedicated muon trigger system both in the barrel and in the endcap regions of CMS. Commissioning of RPC means to ensure that all the services (e.g. HV, LV, gas, cooling, sensors for temperature & humidity and readout system) needed to operate the chambers are working properly. EndCap RPCs are assembled in Pakistan and are commissioned by Pakistani team during 2008-09. The prompt production of c quarkonia is studied in proton-proton collisions at p s = 7 TeV, using data collected by CMS in 2011 corresponding to an integrated luminosity of 4.62 fb􀀀1 . The c mesons are reconstructed through their radiative decays to J= and photon with J= ! + 􀀀. The photons are reconstructed through their conversion in electron-positron pairs in the tracking detector which gives a mass resolution sufficient for resolving cj states. The ratio of the prompt production cross sections of c1 and c2 states, ( c2)= ( c1) has been determined as a function of the J= transverse momentum between 7 and 25 GeV/c.