Higher order corrections and resummation in perturbative QCD[HBNI Th220]

Abstract

This thesis arises in the context of precision physics at hadron colliders. As Large Hadron Collider (LHC) at CERN is close to its Run-3 phase and the experimental measure- ments are rapidly progressing with significant reductions in their uncertainties, it is abso- lutely necessary on theoretical side to deliver equally accurate predictions within Standard Model(SM) and beyond. Perturbative Quantum Chromodynamics (pQCD) plays a cru- cial role for achieving this task through multi-loop and multi-leg computations at high orders in coupling constant. In this context, we present the two-loop QCD corrections to the production of di-Higgs and di-psudo-Higgs in quark annihilation channel. However, the complexity of these computations grows very rapidly with the increase of number of loops and/or external particles. Nevertheless, it has become a reality due to several remarkable developments in due course of time. As the credibility of perturbative series gets affected at kinematic threshold region due to the presence of certain large logarithms, the resummation of the whole perturbative series is required for reliable phenomenolog- ical predictions. In this thesis, we discuss the impact of resummation of the perturbative series at soft-virtual plus next-to soft-virtual (SV+NSV) limit. We present the analytical results of SV+NSV resummed cross section for the case of deep inelastic scattering (DIS), semi-inclusive e + e − annihilation (SIA). The phenomenological results of SV+NSV resummation are provided for the Higgs production cross section in gluon fusion and the Drell-Yan rapidity distribution.