Study of charge multiplicity in hadronic threejet Z decays at LEP.pdfVIP

February 7, 2008 6:59 WSPC/Trim Size: 9in x 6in for Proceedings ISMD˙2002 STUDY OF CHARGE MULTIPLICITY IN HADRONIC 2 THREE-JET Z DECAYS AT LEP ∗ 0 0 2 VLADIMIR A. UVAROV v o Institute for High Energy Physics, Protvino, Russia N (for the DELPHI Collaboration) 5 The mean charge multiplicity in hadronic three-jet Z decays has been measured 1 with the DELPHI detector as a function of the event topology and compared v with recent theoretical calculations. The QCD colour factor ratio CA/CF was 0 determined, and the gluon contribution to this multiplicity was extracted giving a 1 measurement of the mean charge multiplicity of a two-gluon colour-singlet system 0 as a function of the effective c.m. energy covering the range from 16 to 52 GeV. 1 1 2 The radiation of gluons by quarks (other gluons) is proportional to 0 the colour charge CF (CA), where CF and CA are the eigenvalues of the / x quadratic Casimir-operators of the SU (3)C group. Therefore, the com- e- parison of the contributions of quark and gluon jets to the mean particle p multiplicity in hadronic Z decays gives insight into the group structure e of the QCD. These contributions can be studied within the framework of h : the colour dipole model 1,2 which predicts the mean charge multiplicity of v