2019 Impact factor 4.389
Particles and Fields
Eur. Phys. J. C 14, 613-631
DOI 10.1007/s100520000378

Measurement of the strange quark forward-backward asymmetry around the Z0 peak

The DELPHI Collaboration


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

Received: 8 October 1999 / Revised version: 23 February 2000 /
Published online: 18 May 2000 - © Springer-Verlag 2000

A precise measurement of the strange quark forward-backward asymmetry used 3.2M multihadronic events around the Z0 peak collected by the DELPHI experiment from 1992 to 1995. The ring imaging Cherenkov detectors in the barrel and end-cap regions identify high energy charged kaons which tag the s quark. The s quark asymmetry was measured at different centre-of-mass energies; in particular at the Z0 pole

\begin{displaymath}A^0_{s\bar{s}} = 0.1008 \pm 0.0113 \, \mbox{(stat.)} \pm 0.0040 \,
\mbox{(syst.)}, \nonumber

taking the expected d and u quark asymmetries from the Standard Model. The quark flavour fractions are assumed from the Standard Model and the fragmentation process is modelled by JETSET. From the s quark pole asymmetry the electroweak mixing angle was determined:

\begin{displaymath}\sin^2\theta_{eff}^{lept} = 0.2321 \pm 0.0029.\nonumber

The parity violating coupling of the s quark to the Z was determined to be:

\begin{displaymath}A_{s} = 0.909 \pm 0.102\, \mbox{(stat.)} \pm 0.036
\mbox{(syst.)}. \nonumber

Copyright Società Italiana di Fisica, Springer-Verlag 2000