QCD aspects to NLO in the search of some beyond SM scenarios at the hadron colliders

Abstract

The Standard model (SM) of particle physics has been very successful in explaining the fundamental interactions of the elementary particles, seen in the nature. However, the SM itself can not be a fundamental theory for it can not explain certain issues like the hierarchy problem. To address such issues in the SM is the main motivation for many beyond the standard model (BSM) physics scenarios like super symmetry, extra dimensions. With the advent of the Large Hadron Collider (LHC) where the center of mass energy will be and#8730;S = 14 TeV, it will be very much possible to test these theories and to constrain the model parameters. Eventually, the collider phenomenology of the BSM scenarios has gained a lot of interest and a very rich collider signals have been predicted in the literature, most of which are based on a leading order (LO) computation in the perturbation theory. However at the hadron colliders like the LHC, where the gluon fluxes are very high, the QCD corrections will in general be very significant. For the signal cross sections, in addition to the SM subprocesses, many other subprocesses from the BSM sector will enter both at the leading order and nextto- leading order (NLO) levels in the perturbation theory. Hence a naive approximation of the SM K factor to be the same as in the BSM sector is not justifiable and to quantify such higher order (NLO) QCD corrections one needs to perform an explicit computation. These higher order corrections will then be useful in obtaining the bounds on the model parameters from the experimental data. (Chapters 1 and 2). In the warped extra dimension model (RS), we have explicitly computed the NLO QCD corrections to the well known di-photon production process at the LHC, using a semi-analytical two cut-off phase space slicing method which makes it easy to implexi ment various experimental kinematic cuts and the isolation algorithm (for suppressing both QED singularities and the fragmentation photons) on the final state photons...