Determination of the e+e- -> gamma gamma (gamma) cross-section at LEP 2

TL;DR

This paper measures the e+e- -> gamma gamma cross-section at LEP 2 energies, confirming QED's predictions and setting limits on possible new physics deviations.

Contribution

First precise measurement of the e+e- -> gamma gamma cross-section at energies up to 208 GeV, testing QED and constraining beyond Standard Model theories.

Findings

Confirmed QED predictions at highest energies

Set lower limits on deviations from QED

Validated the Standard Model at LEP 2 energies

Abstract

A test of the benchmark QED process e+e- -> gamma gamma (gamma) is reported, using the data collected with the DELPHI detector at LEP 2. The data analysed were recorded at centre-of-mass energies ranging from 161 GeV to 208 GeV and correspond to a total integrated luminosity of 656.4 pb^{-1}. The Born cross-section for the process e+e- -> gamma gamma (gamma) was determined, confirming the validity of QED at the highest energies ever attained in electron-positron collisions. Lower limits on the parameters of a number of possible deviations from QED, predicted within theoretical frameworks expressing physics beyond the Standard Model, were derived.