Eur. Phys. J. C 21, 411-422 (2001)
Determination of the b quark mass at the Z mass scaleThe OPAL Collaboration G. Abbiendi and et al.
Dipartimento di Fisica dell' Università di Bologna and INFN, 40126 Bologna, Italy
(Received: 14 May 2001 / Published online: 17 August 2001 -© Springer-Verlag / Società Italiana di Fisica 2001 )
In hadronic decays of Z bosons recorded with the OPAL detector at LEP, events containing b quarks were selected using the long lifetime of b flavoured hadrons. Comparing the 3-jet rate in b events with that in d,u,s and c quark events, a significant difference was observed. Using calculations for massive quarks, this difference was used to determine the b quark mass in the renormalisation scheme at the scale of the Z boson mass. By combining the results from seven different jet finders the running b quark mass was determined to be . Evolving this value to the b quark mass scale itself yields , consistent with results obtained at the b quark production threshold. This determination confirms the QCD expectation of a scale dependent quark mass. A constant mass is ruled out by 3.9 standard deviations.
© Società Italiana di Fisica, Springer-Verlag 2001