Electroweak and QCD radiative corrections to associated Higgs boson production at the LHC

• Applicant: Hantian Zhang, Ph.D.
• Subject Area: Nuclear and Elementary Particle Physics, Quantum Mechanics, Relativity, Fields
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 551164544

The discovery of the Higgs boson at the Large Hadron Collider (LHC) at CERN in 2012 has confirmed the mechanism of spontaneous electroweak (EW) symmetry breaking. This mechanism is the cornerstone of the Standard Model (SM) of particle physics, which describes the strong (QCD) and EW interactions as a Quantum Field Theory. However, there are fundamental problems that cannot be solved by the SM, such as the origin of dark matter and the matter-antimatter asymmetry of the universe. These problems call for a more fundamental theory beyond the SM (BSM) with new physics effects that we are searching for at the LHC. After ten years efforts, it turns out that new physics searches are still very challenging, and the high-precision comparison between theoretical predictions and experimental measurements is the key to detect subtle new physics effects in the collider observables, particularly in Higgs boson production. Therefore, this project aims to calculate cutting-edge higher-order QCD and EW radiative corrections for two key processes at the LHC: Z boson associated Higgs boson and Higgs boson plus jet production. It contains two parts. Part I aims to analytically calculate the important missing next-to-leading order (NLO) EW virtual corrections to the loop-induced gluon-fusion Z boson associated Higgs boson production. In this context, the boosted region with large Higgs boson transverse momentum (pT) is of great interest, where the fiducial cross sections and pT spectrums are sensitive to both BSM effects and EW corrections. The calculations involve advanced high-energy expansions of two-loop four-point Feynman integrals with internal massive particles such as top quark, Higgs and gauge bosons. To solve these difficult integrals, I will employ differential equation and Mellin-Barnes techniques, along with a novel tool AsyInt that I have developed. The results will be instrumental to the cutting-edge studies of Higgs boson properties. Part II aims to provide the real-real-virtual (RRV) corrections in the third order (N3LO) QCD to Higgs boson plus jet production within the OpenLoops framework, a widely used software of which I am a co-author. For phenomenological studies, it is crucial to have high-precision RRV contributions, which require one-loop six-point amplitudes in the challenging double-unresolved real-radiation region. To achieve this, I propose to develop an analytic all-order expansion in the double-unresolved limit. This expansion will enable further RRV corrections to a wide spectrum of LHC processes. The completion of this project will advance the frontier of precision physics. The new results will allow us to test whether the forthcoming LHC measurements of these two processes align with the SM predictions or deviate toward new physics scenarios.

• DFG Programme: WBP Position