Z-boson production with two unobserved, back-to-back, hard photons at LEP

TL;DR

This paper investigates the production of Z bosons accompanied by two hard photons that escape detection, measuring cross sections at LEP energies and confirming consistency with the Standard Model predictions.

Contribution

It provides the first measurement of the double-radiative process with undetected photons at LEP energies, testing Standard Model predictions in this regime.

Findings

Measured cross sections align with Standard Model expectations

First experimental study of Z + two undetected photons at LEP

Data collected at energies between 188.6 and 209.2 GeV

Abstract

The double-radiative process e+e- -> Z gamma gamma -> q q~ gamma gamma, where the two hard photons escape detection at low polar angles into opposite directions, is studied in 0.62/fb of data collected with the L3 detector at LEP at centre-of-mass energies between 188.6GeV and 209.2GeV. The cross sections are measured and found to be consistent with the Standard Model expectations.