2019 Impact factor 4.389
Particles and Fields
Eur. Phys. J. C 12, 209-224
DOI 10.1007/s100529900227

Determination of $P(c \rightarrow D^{*+})$ and $BR(c \rightarrow l^+)$ at LEP 1

The DELPHI Collaboration

P.Abreu21 - et al.

21 LIP, IST, FCUL - Av. Elias Garcia, 14-1o, PT-1000 Lisboa Codex, Portugal

Received: 1 June 1999 / Published online: 8 December 1999

Abstract
The probability $P(c \rightarrow D^{*+})$ that a charm quark fragments into a D*+ meson and the $c \rightarrow l^+$ semileptonic branching fraction were measured in $Z^0\ $ decay into $c\bar{c}$ events.
From the analysis of 3.5 Million $Z^0\ $ events collected from 1992 to 1995, a sample of charm meson decays with $81\%$ $c\bar{c}$ purity was selected. The product of the $c \rightarrow D^{*+}$ fragmentation probability times the $D^{*+}\rightarrow D^0\pi^+$ branching fraction was measured to be:
$P(c \rightarrow D^{*+})\cdot BR(D^{*+}\rightarrow D^0\pi^+) = 0.174\pm0.010(stat) \pm0.004(syst) \; .$
Using the world averaged value for $BR(D^{*+}\rightarrow D^0\pi^+)$, the fragmentation probability is inferred:
$P(c \rightarrow D^{*+}) = 0.255\pm0.015(stat) \pm0.006(syst) \pm0.005 (syst.BR) \; .$
From the same sample, $1828\pm 51$ identified leptons in the opposite hemisphere were selected. From this sample, the charm semileptonic branching fraction was measured to be:
$BR(c \rightarrow l^+) = 0.0958\pm0.0042(stat) \pm0.0028(syst) \; .$


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