Measurement of triple gauge WWgamma couplings at LEP2 using photonic events

TL;DR

This study measures the W W gamma gauge couplings at LEP2 by analyzing photon events with missing energy, confirming Standard Model predictions and constraining possible deviations in the couplings.

Contribution

It provides the first experimental constraints on W W gamma couplings using photon events at LEP2 energies.

Findings

Measured Delta(kappa_gamma) close to zero with uncertainties

Measured lambda_gamma consistent with zero within errors

Results agree with Standard Model predictions

Abstract

A study of events with photons and missing energy has been performed with the data sample obtained with the ALEPH detector at centre-of-mass energies from 161 to 184 GeV,corresponding to a total integrated luminosity of about 80 pb**-1. The measured distributions are in agreement with Standard Model predictions, leading to constraints on W W gamma gauge coupling parameters Delta(kappa_gamma) and lambda_gamma. The results from the fit to the cross sections and to the energy and angular distributions of the photons are: Delta(kappa_gamma) = 0.05 +1.15/-1.10 (stat) +/- 0.25 (syst) lambda_gamma = 0.05 +1.55/-1.45 (stat) +/- 0.30 (syst)