We acknowledge in particular the support of Austrian Federal Ministry of Science and Traffics, GZ 616.364/2-III/2a/98, FNRS{FWO, Belgium, FINEP, CNPq, CAPES, FUJB and FAPERJ, Brazil, Czech Ministry of Industry and Trade, GA CR 202/96/0450 and GA AVCR A1010521, Danish Natural Research Council, Commission of the European Communities (DG XII), Direction des Sciences de la Matiere, CEA, France, Bundesministerium fur Bildung, Wissenschaft, Forschung und Technologie, Germany, General Secretariat for Research and Technology, Greece, National Science Foundation (NWO) and Foundation for Research on Matter (FOM), The Netherlands, Norwegian Research Council, State Committee for Scientific Research, Poland, 2P03B06015, 2P03B1116 and SPUB/P03/178/98, JNICT-Junta Nacional de Investigaçao Cientifica e Tecnologica, Portugal, Vedecka grantova agentura MS SR, Slovakia, Nr. 95/5195/134, Ministry of Science and Technology of the Republic of Slovenia, CICYT, Spain, AEN96-1661 and AEN96-1681, The Swedish Natural Science Research Council, Particle Physics and Astronomy Research Council, UK, Department of Energy, USA, DE-FG02{94ER40817.

The probability P(c→D∗+) that a charm quark fragments into a D∗+ meson and the c→l+ semileptonic branching fraction were measured in Z0 decay into c¯c events. \par % A double tag method based % on the detection of exclusively reconstructed D mesons % accompanied by a slow pion or a lepton in the opposite hemisphere was used.\par From the analysis of 3.5 Million Z0 events collected from 1992 to 1995, a sample of charm meson decays with 81%c¯c purity was selected. % In this sample, a signal of 2371±140 low momentum pions % originating from a D∗± decay in the opposite hemisphere % was observed. The product of the c→D∗+ fragmentation probability times the D∗+→D0π+ branching fraction was measured to be: P(c→D∗+)⋅BR(D∗+→D0π+)=0.174±0.010(stat)±0.004(syst). Using the world averaged value for BR(D∗+→D0π+), the fragmentation probability is inferred: P(c→D∗+)=0.255±0.015(stat)±0.006(syst)±0.005(syst.BR). From the same sample, 1828±51 identified leptons in the opposite hemisphere were selected. From this sample, the charm semileptonic branching fraction was measured to be: BR(c→l+)=0.0958±0.0042(stat)±0.0028(syst).

DELPHI Collaboration: et al.

Peer reviewed