Measurement of the strange quark forward-backward asymmetry around the Z(0) peak

A precise measurement of the strange quark forward-backward asymmetry used 3.2 M multihadronic events around the Z(0) 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 Z(0) pole A(s (s) over bar)(0) = 0.1008 +/- 0.0113 (stat.) +/- 0.0040 (syst.), 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: sin(2) theta(eff)(lept) = 0.2321 +/- 0.0029. The parity violating coupling of the s quark to the Z was determined to be: A(s) = 0.909 +/- 0.102 (stat.) +/- 0.036(syst.).