Photon pair production at flavour factories with per mille accuracy

TL;DR

This paper introduces a highly precise QED calculation for photon pair production in electron-positron annihilation, achieving 0.1% accuracy to support advanced luminosity measurements at flavour factories.

Contribution

It develops a novel matching of NLO corrections with a QED Parton Shower in the BabaYaga generator, enabling ultra-precise simulations of photon pair production.

Findings

Achieved 0.1% theoretical accuracy in photon pair production calculations.

Demonstrated the impact of radiative corrections on experimental observables.

Provided a new tool for high-precision luminosity monitoring at colliders.

Abstract

We present a high-precision QED calculation, with 0.1% theoretical accuracy, of two photon production in $e^+ e^-$ annihilation, as required by more and more accurate luminosity monitoring at flavour factories. The accuracy of the approach, which is based on the matching of exact next-to-leading order corrections with a QED Parton Shower algorithm, is demonstrated through a detailed analysis of the impact of the various sources of radiative corrections to the experimentally relevant observables. The calculation is implemented in the latest version of the event generator BabaYaga, available for precision simulations of photon pair production at $e^+ e^-$ colliders of moderately high energies.