W pair production cross-section and W branching fractions in e+e- interactions at 189 GeV

TL;DR

This study measures the W+W- production cross-section and W decay branching fractions at 189 GeV, confirming Standard Model predictions and deriving the CKM matrix element |V_{cs}| with high precision.

Contribution

First measurement of W+W- cross-section and W decay branching fractions at 189 GeV using DELPHI data, with results consistent with the Standard Model.

Findings

W+W- cross-section measured as 15.83 pb

W decay branching fractions agree with Standard Model

|V_{cs}| determined as 1.001 with uncertainties

Abstract

The cross-section for the process e+e- -> W+W- has been measured with the data sample collected by DELPHI at an average centre-of-mass energy of 189 GeV and corresponding to an integrated luminosity of 155 pb^{-1}. Based on the 2392 events selected as WW candidates, the cross-section for the doubly resonant process e+e- -> W+W- has been measured to be 15.83 +- 0.38 (stat) +- 0.20 (syst) pb. The branching fractions of the W decay were also measured and found to be in good agreement with the Standard Model expectation. From these a value of the CKM mixing matrix element |V_{cs}| = 1.001 +- 0.040 (stat) +- 0.020 (syst) was derived.