Detector Control System for CMS Endcap RPCs and Cross Section Measurement of $t\bar{t}$ dileptonic channel with the CMS Detector at $\sqrt{s}$ = 8 $TeV$

The Resistive Plate Chamber Endcap(RE) system consists of 432 double-gap chambers equipped with about 1296 front-end boards. Safe and correct operation of RE system requires a sophisticated and complex online Detector Control System(DCS), which should be able to control and monitor 2$\times$$10^{3}$ hardware devices spanned on an area of about 2000 $m^{2}$. DCS of RE system monitors, acquires and stores about $10^{3}$ parameters obtained from the detector, electronics, power system, gas, and cooling systems. The RE DCS system and its performance during the 2007 and 2008 CMS cosmic runs, will be discussed in this thesis. The $\tt$ pair production cross section is measured in 2012 proton-proton collisions at $\sqrt{s}$ = 8 $TeV$ using 19.7 $fb^{-1}$ of integrated luminosity data sample of the CMS experiment. The measurement is done by using events in which we have two high $p_{T}$ leptons (muons or electrons), missing transverse energy and atleast one jet identified as $b$-quark, in the final state. The cross section was value \begin{equation*} \sigma_{\tt} = 248.530 \pm 1.028 (stat.) \pm 8.202 (syst.) pb \end{equation*} is in agreement with theoretical predictions, also individual cross section for each dilepton channel are provided.