# Gordon Research Seminar in Particle Physics: Pushing the Frontiers of Particle Physics During the LHC Run II Era

Jun 24 – 25, 2017
Hong Kong University of Science and Technology (HKUST)
Asia/Hong_Kong timezone

## top-quark mass from diphoton mass spectrum

Jun 24, 2017, 8:15 PM
15m
Hong Kong University of Science and Technology (HKUST)

Hiroshi Yokoya

### Description

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.

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