A precise measurement of the left-right cross section asymmetry in Z boson production

Abstract

The authors present a precise measurement of the left-right cross section asymmetry (A{sub LR}) for Z boson production by e{sup +}e{sup {minus}} collisions. The measurement was performed at a center-of-mass energy of 91.26 GeV with the SLD detector at the SLAC Linear Collider (SLC). The luminosity-weighted average polarization of the SLC electron beam was (63.0 {+-} 1.1)%. Using a sample of 49,392 Z decays, they measure A{sub LR} to be 0.1628 {+-} 0.0071 (stat.) {+-} 0.0028(syst.) which determines the effective weak mixing angle to be sin{sup 2} {theta}{sub W}{sup eff} = 0.2292 {+-} 0.0009(stat.) {+-} 0.0004(syst.). They combine this result with the result obtained in 1992 and obtain sin{sup 2} {theta}{sub W}{sup eff} = 0.2294 {+-} 0.0010, which constitutes the best measurement of sin{sup 2} {theta}{sub W}{sup eff} in a single experiment presently available.