A measurement of sin 2θ w from the charge asymmetry of hadronic events at the Z 0 peak

Abstract

The weak mixing angle has been measured from the charge asymmetry of hadronic events with two different approaches using the DELPHI detector at LEP. Both methods are based on a momentum-weighted charge sum to determine the jet charge in both event hemispheres. In a data sample of 247 300 multihadronic Z 0 decays a charge asymmetry of 〈 Q F 〉 − 〈 Q B 〉 = −0.0076±0.0012(stat.)±0.0005(exp. syst.)±0.0014(frag.) and a raw forward-backward asymmetry of A raw FB = −0.0109±0.0020(stat.)±0.0010(exp. syst.)±0.0017(frag.) have been measured. This result corresponds to a value of sin θ eff =0.2345±0.0030(exp.)±0.0027(frag.), sin 2θ MS =0.2341±0.0030( exp.)±0.0027( frag.) and to sin 2 θ W =1− m 2 W / m 2 Z =0.2299± 0.0030(exp.)±0.0027(frag.)±0.0028(theor.). The experimental error is the quadratic sum of the statistical and the experimental systematic error and the theoretical error originates from a value of m t =130±40 GeV/ c 2 and a range of m H from 45 GeV/ c 2 to 1000 GeV/ c 2.