Study of Data Driven performance evaluation method for CMS RPC Trigger system using 2011 data at LHC

The long awaited Large Hadron Collider (LHC) experiment started last year in March, 2010 and it is successfully collecting data at center of mass energy 7TeV at present. The Compact Muon Solenoid (CMS) is one of the four experiments which is getting and analyzing the results of the collision of protons at LHC. The collision of proton bunches occur at CMS detector every 25 ns that is with a frequency of 40 MHz. So in order to handle such a large stream of data, the first stage of analysis is performed by the dedicated trigger system. In case of CMS experiment the trigger system is divided into two stages: the Level-1 Trigger, based on hardare and custom electronics and High Level Triggers which are purely software based. The Resistive Plate Chambers (RPC) which contributes the main part of the CMS muon system along with Drift Tube Detectors (DT) in barrel and Cathode Strip Chambers (CSC) in endcaps, is a part of the Level-1 Muon Trigger System. The informations transmitted from the three subsystems are collected by the Global Muon trigger (GMT) Board and merged according to a sophisticated algorithm. A method for evaluating the RPC system trigger efficiency with data from p-p collision has been developed by using the features of GMT. The GMT candidates containing RPC information are used for efficiency evaluation in two ways: on the one hand using the bare GMT candidates and on the other hand using the GMT candidates with DT measurement as seed for muon system track reconstruction. The results of the study with the real data of 2010 are shown and discussed here along with the comparison of Monte Carlo results.