Nadeesha Wickramage

After the Phase-2 high-luminosity upgrade to the Large Hadron Collider (LHC), the collision rate and therefore the background rate will significantly increase, particularly in the high $\eta$ region. To improve both the tracking and triggering of muons, the Compact Muon Solenoid (CMS) Collaboration plans to install triple-layer Gas Electron Multiplier (GEM) detectors in the CMS muon endcaps. Demonstrator GEM detectors were installed in CMS during 2017 to gain operational experience and perform a preliminary investigation of detector performance. We present the results of triple-GEM detector performance studies performed in situ during normal CMS and LHC operations in 2018. The distribution of cluster size and the efficiency to reconstruct high $p_T$ muons in proton--proton collisions are presented as well as the measurement of the environmental background rate to produce hits in the GEM detector.

A measurement of the transverse momentum distribution of Z bosons decaying to dimuons in pp collisions at s=8 TeV is reported. The results are obtained using a data sample collected by the CMS experiment at the LHC, corresponding to an integrated luminosity of 18.4 pb-1. An overall agreement with the theoretical predictions is observed, however no single model can reproduce the transverse momentum distributions over the whole accessible range.

In this paper an analysis is presented on performance of RPC chambers installed in the cosmic ray test stand at ISR, CERN. The currents of RPC chambers are studied as a function of environmental parameters such as temperature, humidity and pressure, which are important for the operation of the RPC detector system at CMS. A neural network approach has been used to analyze the data and to build a model using experimental measurements and combining the results of the simulations.