A Measurement of the Rate of Charm Production in W Decays

TL;DR

This paper measures the charm quark production rate in W boson decays at LEP, confirming Standard Model predictions and estimating the CKM matrix element Vcs with high precision.

Contribution

It provides a novel measurement of the charm production ratio in W decays and determines the CKM matrix element Vcs using LEP data.

Findings

Charm production ratio Rc^W = 0.481 +- 0.042 (stat.) +- 0.032 (syst.)

Vcs = 0.969 +- 0.058

Results are compatible with Standard Model expectations.

Abstract

Using data recorded at centre-of-mass energies around 183 GeV and 189 GeV with the OPAL detector at LEP, the fundamental coupling of the charm quark to the W boson has been studied. The ratio Rc^W = Gamma(W -> cX)/Gamma(W -> hadrons) has been measured from jet properties, lifetime information, and leptons produced in charm decays. A value compatible with the Standard Model expectation of 0.5 is obtained: Rc^W = 0.481 +- 0.042(stat.) +- 0.032(syst.). By combining this result with measurements of the W boson total width and hadronic branching ratio, the magnitude of the CKM matrix element Vcs is determined to be |Vcs| = 0.969 +- 0.058.