Qcd corrections to the g olden decay channel of the h iggs boson

Abstract

Precision studies within the Higgs sector of the Standard Model are crucial to deepen our newlineunderstanding of the fundamental particle interactions and uncovering new physics phenomena newlineAbstract newlinebeyond the Standard Model, thereby guiding us towards a more comprehensive understanding newlineof the universe. In this context, future colliders aim to provide highly precise experimental newlinemeasurements of the properties and couplings of the Higgs boson. To fully leverage the potential newlineof these precision machines, it is crucial to minimize theoretical errors in the Higgs sector newlineobservables, such as production and decay rates, to at least match the level of experimental newlineuncertainties. newlineReducing theoretical uncertainties involves including higher-order terms in perturbative newlinecalculations of the observables. Central to these calculations are Feynman integrals, which form newlinethe backbone of the theoretical framework. newlineIn this thesis, we focus on providing precise predictions for the observables associated with newlineone of the most important decay channels of the Higgs boson, the Golden decay channelquot. Our newlinework improves theoretical predictions for the partial decay width of this channel, specifically newlinethe H and#8594; Z (and#8727;) Z (and#8727;) and#8594; e + e and#8722; µ + µ and#8722; channel, by incorporating NNLO mixed QCD-electroweak newlinecorrections in the perturbation theory. The entire calculation of the decay amplitude at O(and#945;and#945; s ) newlineis performed systematically following the conventional workflow of multi-loop calculations. newlineThis approach involves the application of the Feynman rules, the tensor decomposition of newlinecontributing amplitudes, and the utilization of integration-by-parts identities to express the newlineamplitudes in terms of master integrals. newlineWe describe the full analytical evaluation of these two-loop master integrals, specifically newlinethose appearing in the O(and#945;and#945; s ) corrections to the HZZ vertex with both Z-bosons being off-shell, newlineemploying the method of differential equations. The calculation retains full dependence on the newlinemasses of all the particles, including those in the loop. Despite encoun