Search for the SM Higgs boson in the H -> WW -> l$v$jj & Probe of WW Production in Vector Boson Fusion Topology in the CMS Experiment at the LHC

The Large Hadron Collider (LHC) at CERN is the world’s largest and highest energy particle accelerator. It was built with the aim of allowing physicists to test the predictions of the Standard Model (SM) of particle physics, and particularly for the existence of the hypothesized Higgs boson; and to search for new particles predicted by theories beyond the SM. The Compact Muon Solenoid (CMS) is one of the main experiments at the LHC. The main objective of the CMS detector is to perform research in the experimental frontier of High Energy Physics, which is made possible because of the excellent running of LHC. This thesis aims to work on two fundamental problems of the SM. First, a search for the SM Higgs boson ($H$) is carried out in $H$ decaying to $WW$ in the semileptonic final state (H → WW → l$ν$jj, with l being $e$ or $\mu$) with the CMS detector at the LHC. Further, a measurement of WW production in vector boson fusion (VBF) topology is also carried out with the CMS detector at the LHC. Both these analyses are performed using data recorded at $\sqrt{s}$ = 8 TeV in 2012 corresponding to an integrated luminosity of 19.3 fb$^{-1}$ The decay channel, H → WW → l$ν$jj, is sensitive to higher Higgs boson masses (≥ 200 GeV) and is one of the leading channels in the CMS experiment for search of the SM Higgs boson in the higher mass range. The analysis selects events with one well-identified lepton, large missing energy and at least two high transverse momentum jets. A multivariate discriminant is designed in order to control the background while preserving, as much as possible, the signal component. The main background contaminating the signal region is $W$ + $jets$, which has much higher production cross-section than that of the Higgs boson, and hence it is a major experimental challenge. This analysis imposes limits on the SM Higgs cross section in the high mass region of the Higgs boson, as well as on the heavy Higgs boson coupling and branching ratios in the BSM framework. This thesis also reports a first measurement on vector boson scattering in the semileptonic decay mode of the $WWWW$ interaction. The final states consists of a lepton, missing energy, two central jets and two forward jets. A special jet selection technique is developed with emphasis on having higher signal efficiency. We extract the VBF signal yield from an unbinned maximum likelihood fit to the dijet invariant mass distribution in the data. This work can serve as a baseline for future $WW$ scattering analysis.