IR-improved DGLAP-CS parton shower effects in W + jets at √ s = 7, 8, and 13 TeV.

The invention and development of collider physics in the twentieth century provides us with opportunities to determine which particles exist in nature, their properties, and the ways they interact with each other. The discovery of the Higgs boson, the last undetected particle predicted in the Standard Model (SM) of Particle Physics, brought a lot of excitement to the international physics community. The SM is based on the gauge group SU(3)QCD ×SU(2)weak ×U(1)hypercharge. Through a process called Spontaneous Symmetry Breaking (SSB), it is broken down to SU(3)QCD × U(1)EM at a scale around 247 GeV [1]. Since the SM is a renormalizable theory with 27 parameters, we can test it by performing enough experiments with enough precision. It is possible to improve the infrared aspects of the standard treatment of the DGLAP-CS evolution theory to take into account a large class of higher-order corrections that significantly improve the precision of the theory for any given level of fixed-order calculation of its respective kernels [2]. We use recently introduced MC realizations of IR-improved DGLAP-CS parton showers to study the attendant improvement effects in W + jets at the LHC in the MG5 aMC@NLO framework for exact O(αs) corrections. Implementation of the new IR-improved kernels in the framework of HERWIG6.5 yields the new IR-improved parton shower MC HERWIRI1.031 [3]. Events are showered by HERWIG6.5 and HERWIRI1.031 with PTRMS = 2.2 GeV and PTRMS = 0 GeV, respectively. We compare our results with the available LHC data and discuss the corresponding phenomenological implications. In Chapter Four we have used the latest results provided by CMS and ATLAS for 7 TeV. In Chapter Five we have used the CMS results published in 2017 for 8 TeV.