Precise top-quark mass from the diphoton mass spectrum

TL;DR

This paper develops a precise method to determine the top-quark mass by analyzing the diphoton mass spectrum near the $tar t$ threshold, incorporating bound-state effects and higher-order corrections.

Contribution

It introduces a calculation of the diphoton spectrum including $tar t$ bound-state effects with NLO and partial NNLO corrections, enabling a direct top-quark mass measurement.

Findings

Predicted diphoton spectrum shape with high accuracy

Demonstrated the observable's potential for top-quark mass determination

Included bound-state effects in the amplitude calculation

Abstract

We calculate the $gg\to\gamma\gamma$ amplitude by including the $t\bar t$ bound-state effects near their mass threshold. In terms of the non-relativistic expansion of the amplitude, the LO contribution is an energy-independent term in the one-loop amplitude. We include the NLO contribution described by the non-relativistic Green function and part of the NNLO contribution. Despite a missing NLO piece which can be accomplished with the two-loop-level amplitude via massive quarks, the shape of the diphoton mass spectrum is predicted with a good accuracy. Thanks to the simple and clean nature of the observable, its experimental measurement can be a direct method to determine the short-distance mass of the top quark at hadron colliders.