A measurement of the relative decay rate of the charm quark into leptons

The inclusive rate of leptons produced from charmed particle decays
(from Z -> charm anticharm) has been measured using a data
sample of four million hgadronic Z decays recorded by the ALEPH
experiment at LEP from 1991 to 1995. The analysis uses a double-tag
and is self-calibrating, i.e. it makes minimum use of the Monte
Carlo simulated information. Each event is divided into two
hemispheres; hemispheres containing charm quarks are identified
with a NEural Network anlaysis method. Lepton candidates are then
searched for in the opposite hemisphere. Based on fully
reconstructed D candidates, a value of BR(c -> l + X) = 9.09 +/-
0.61 % (l = e or mu) is obtained. The uncertainy includes both the
statistical and systematic components.