Measurement of W-pair production in e+e- collisions at 183 GeV

TL;DR

This paper reports on the measurement of W-pair production cross sections and decay branching ratios at 183 GeV, confirming Standard Model predictions and constraining possible undetectable decay modes.

Contribution

It provides precise measurements of W-pair production and decay properties at 183 GeV, including the W decay branching ratio and CKM matrix element |Vcs|, consistent with the Standard Model.

Findings

W-pair production cross section measured as 15.57 pb

W decay branching ratio into hadrons is 68.93%

Results agree with Standard Model predictions

Abstract

The production of W+W- pairs is analysed in a data sample collected by ALEPH at a mean centre-of-mass energy of 182.7 GeV, corresponding to an integrated luminosity of 57 pb-1. Cross sections are given for different topologies of W decays into leptons or hadrons. Under Standard Model assumptions for the W-pair production and decay, the W-pair cross section is measured to be 15.57+-0.62(stat.)+-0.29(syst.) pb. Using also the W-pair data samples collected by ALEPH at lower centre-of-mass energies, the decay branching ratio of the W boson into hadrons is measured to be B(W->hadrons)= 68.93+-1.21(stat.)+-0.51(syst.)%, allowing a determination of the CKM matrix element |Vcs|= 1.043 +- 0.058(stat.) +- 0.026(syst.). The agreement of the cross sections with the Standard Model prediction allows a limit to be set on the W decay rate to undetectable final states.