2018 Impact factor 4.843
Particles and Fields

Eur. Phys. J. C 16, 185-210
DOI 10.1007/s100520000391

QCD studies with \ensuremath{\ensuremath{\mathrm{e^+e^-}}}

The OPAL Collaboration

G. Abbiendi2 - et al.

2 Dipartimento di Fisica dell' Università di Bologna and INFN, 40126 Bologna, Italy

Received: 17 December 1999 / Published online: 18 May 2000 - © Springer-Verlag 2000

Abstract
We have studied hadronic events from $\ensuremath{\mathrm{e^+e^-}} $annihilation data at centre-of-mass energies of $\ensuremath{\sqrt{s}} =$172, 183 and 189 GeV. The total integrated luminosity of the three samples, measured with the OPAL detector, corresponds to 250 pb-1.
We present distributions of event shape variables, charged particle multiplicity and momentum, measured separately in the three data samples. From these we extract measurements of the strong coupling \ensuremath{\alpha_s }, the mean charged particle multiplicity \ensuremath{\langle
n_{\mathrm{ch}}\rangle} and the peak position \ensuremath{\xi_0} in the $\ensuremath{\xi_p} =\ln(1/\ensuremath{x_p} )$distribution.
In general the data are described well by analytic QCD calculations and Monte Carlo models. Our measured values of \ensuremath{\alpha_s }, \ensuremath{\langle
n_{\mathrm{ch}}\rangle} and \ensuremath{\xi_0} are consistent with previous determinations at \ensuremath{\sqrt{s}}= \ensuremath{M_{\mathrm{Z^0}}}.


Copyright Società Italiana di Fisica, Springer-Verlag 2000