QCD Radiative Corrections to Higgs Physics

The central part of this thesis deals with the quantum chromodynamics (QCD) radiative corrections to some important observables associated with the Drell-Yan, scalar and pseudo-scalar Higgs boson productions at next-to-next-to-next-to-leading order (N$^{3}$LO) aiming to uplift the accuracy of theoretical results. The Higgs bosons are produced dominantly at the Large Hadron Collider (LHC) via gluon fusion through top quark loop, while one of the subdominant ones takes place through bottom quark annihilation whose contribution is equally important and must be included in precision studies. Here, we have computed analytically the inclusive cross section of the Higgs boson produced through this channel under the soft-virtual (SV) approximation at N$^{3}$LO QCD following an elegant formalism. Moreover, the differential rapidity distribution is another most important observable, which is expected to be measured in upcoming days at the LHC. This immediately calls for very precise theoretical predictions. The analytical expressions of the SV corrections to this observable at N$^{3}$LO for the Higgs boson, produced through gluon fusion, and leptonic pair in Drell-Yan (DY) production are computed and the numerical impacts of these results are demonstrated. In addition, the CP-odd/pseudo-scalar Higgs boson, which is one of the most prime candidates in BSM scenarios, is studied in great details, taking into account the QCD radiative corrections. We have computed the analytical results of the three loop QCD corrections to the pseudo-scalar Higgs boson production and consequently, obtained the inclusive production cross section at N$^{3}$LO under SV approximation. These indeed help to reduce the theoretical uncertainties arising from the renormalisation and factorisation scales and undoubtedly, improve the reliabilities of the theoretical results.