Abstract
We present a calculation of the helicity amplitudes for the process gg → γγ in three-loop massless QCD. We employ a recently proposed method to calculate scattering amplitudes in the ’t Hooft-Veltman scheme that reduces the amount of spurious non-physical information needed at intermediate stages of the computation. Our analytic results for the three-loop helicity amplitudes are remarkably compact, and can be efficiently evaluated numerically. This calculation provides the last missing building block for the computation of NNLO QCD corrections to diphoton production in gluon fusion.
Highlights
JHEP02(2022)153 from NNLO, the gg partonic channel opens up
Being gluon induced one expects large radiative corrections. This has spurred many investigations, which upgraded the precision in this channel to next-to-leading order (NLO) in QCD, i.e. to O(αs3) [18, 19]
Given the ever-increasing experimental precision on diphoton measurements [20, 21], it becomes interesting to try and push the theoretical precision even further and consider NNLO corrections to the gg → γγ process. While this is desirable for a variety of Large Hadron Collider (LHC) analyses, it is of particular importance for Higgs studies
Summary
We consider virtual QCD corrections to the production of two photons through gluon fusion g(p1) + g(p2) → γ(−p3) + γ(−p4) ,. We adopt the ’t Hooft-Veltman (tHV) scheme [31], i.e. we perform computations for generic d but we constrain all the external particles and their polarisations to live in the physical d = 4 subspace. This allows us to simplify the calculation compared to the Conventional Dimensional Regularisation (CDR) case, where internal and external degrees of freedom are treated as d-dimensional. We have extracted the leadin√g-order electroweak coupling written in terms of the fine structure constant α, where e = 4πα is the unit of electric charge.
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