A Measurement of the Rate of Charm Production in W Decays.pdf

a r X i v : h e p - e x / 0 0 0 9 0 2 0 v 1 7 S e p 2 0 0 0 EUROPEAN ORGANIZATION FOR NUCLEAR RESEARCH CERN-EP-2000-100 July 20th 2000 A Measurement of the Rate of Charm Production in W Decays The OPAL Collaboration Abstract Using data recorded at centre–of–mass energies around 183GeV and 189GeV with the OPAL detector at LEP, the fundamental coupling of the charm quark to the W boson has been studied. The ratio RWc ≡ Γ (W → cX)/Γ (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: RWc = 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. (Submitted to Physics Letters B) The OPAL Collaboration G.Abbiendi2, K.Ackerstaff8, C.Ainsley5, P.F. A?kesson3, G.Alexander22, J.Allison16, K.J.Anderson9, S.Arcelli17, S.Asai23, S.F.Ashby1, D. Axen27, G.Azuelos18,a, I. Bailey26, A.H. Ball8, E. Barberio8, R.J. Barlow16, S. Baumann3, T.Behnke25, K.W.Bell20, G.Bella22, A. Bellerive9, G. Benelli2, S. Bentvelsen8, S. Bethke32, O.Biebel32, I.J. Bloodworth1, O.Boeriu10, P.Bock11, J. Bo?hme14,h, D.Bonacorsi2, M. Boutemeur31, S. Braibant8, P. Bright-Thomas1, L. Brigliadori2, R.M.Brown20, H.J. Burckhart8, J. Cammin3, P.Capiluppi2, R.K. Carnegie6, A.A. Carter13, J.R.Carter5, C.Y. Chang17, D.G.Charlton1,b, P.E.L. Clarke15, E.Clay15, I. Cohen22, O.C.Cooke8, J. Couchman15, C.Couyoumtzelis13, R.L. Coxe9, A.Csilling15,j , M.Cuffiani2, S.Dado21, G.M.Dallavalle2 , S.Dallison16, A. de Roeck8, E. de Wolf8, P. Dervan15, K.Desch25, B. Dienes30,h, M.S.Dixit7, M.Donkers6, J.Dubbert31, E. Duchovni24, G.Duckeck31, I.P. Duerdoth16, P.G. Estabrooks6, E. Etzion22, F. Fabbri2, M. Fanti2, L. Feld10, P. Ferrari12, F. Fiedler8, I. Fleck10, M.Ford5, A. Frey8, A. Fu?rtjes8, D.I. Futyan16, P.Gagnon12, J.W.Gary4