Electroweak corrections to $gg\rightarrow γγ$

Abstract

We present the electroweak corrections for the production of a photon pair through gluon fusion, focusing on the contribution from the first two generations of quarks. The two-loop amplitude is calculated using a series of projection operators which define scalar form factors. In order to evaluate the Master Integrals which appear in this process we employ both generalized polylogarithms and Chen-iterated integrals. In order to perform a phenomenological study we develop a semi-numerical evaluation of the Master Integrals employing a fitting procedure to speed up the evaluation of burdensome higher weight contributions. We present results for the LHC, finding corrections of around a couple of percent to the leading order $gg \rightarrow γγ$ process. Our results are implemented into the parton-level Monte Carlo code \texttt{MCFM}.

Figures (8)

• Figure 1: Leading Order diagram for the $gg\to\gamma\gamma$ process.
• Figure 2: Feynman diagrams associated with the relevant W-type topologies. Propagators marked in red are massive.
• Figure 3: Break-down of the fitting region for each relevant topology, each color represents a unique fitting region.
• Figure 4: Heat map of the relative fitting error for the relevant weight of integral 31 of topology $\textnormal{P}_\textnormal{III}$ in region B.
• Figure 5: Heat map of the relative fitting error for the relevant weight of integral 32 of topology $\textnormal{N}_\textnormal{II}$ in region $\textnormal{C}_{\textnormal{1}}$.