Research and development studies for CMS at the Super LHC conditions and inclusive search for new physics at CMS with jets and missing momentum signature

This thesis is composed of two independent parts. The first part is devoted to Hadronic Endcap Calorimeter R&D; studies for the Large Hadron Collider (LHC) higher luminosity conditions, whereas in the second part a search for new physics at the Compact Muon Solenoid (CMS) experiment is presented. After a brief introduction to the LHC and the CMS experiment, in the first part R&D; studies on the active material of Hadronic Endcap (HE) Calorimeter for Compact Muon Solenoid Detector Upgrade are presented. We performed radiation damage and beam test studies on several wavelength shifter materials, and found that the p-terphenyl deposited quartz plates give improved light efficiency and they are also radiation hard. As a result we propose to substitute the current HE scintillator tiles with p-terphenyl deposited quartz plates for the higher luminosity era of the Large Hadron Collider. In the second part, an inclusive search for new physics with the jets and missing momentum signature at the Large Hadron Collider is presented for 36 pb$^{-1}$ data collected by the Compact Muon Solenoid detector from March 2010 to November 2010. The emphasis was put on jet resolution measurements for the QCD background estimation with a photon-jet data sample. We did not observe an excess above the background, and thus derived upper limits in the context of R-parity conserving Constrained Minimal Supersymmetric Standard Model (CMSSM) and, more generally in the simplified model spectra. In CMSSM, depending on squark and gluino masses a 95% confidence level (CL) upper limit for cross section of 2-3 pb is obtained, and gluino masses below 500 GeV are excluded with 95% CL for squarks with mass below 1 TeV. In simplified models, depending on the decay chain and mass of the new particles which are pair-produced and decay to to either one or two jets and a dark matter candidate, a 95% CL upper limit on the production cross section in the 0.5-30 pb range is obtained.