Light Quark Fragmentation in Polarized Z{sup 0} Decays at SLD

Abstract

We report results on two physics topics from the SLD experiment at the SLAC Linear Collider, using our full sample of 550,000 events of the type e + e − → Z 0 → qq. The electron beam was polarized, enabling the quark and antiquark hemispheres to be tagged in each event. One physics topic is the first study of rapidities signed such that positive rapidity is along the quark rather than antiquark direction. Distributions of ordered differences in signed rapidity between pairs of particles are analyzed, providing the first direct observation of baryon number ordering along the qq axis. The other topic is the first direct measurement of A s , the parity-violating coupling of the Z 0 to strange quarks, by measuring the left-right forward-backward production asymmetry in polar angle of the tagged s quark. We obtain A s = 0.895 ± 0.066(stat.) ± 0.062(syst.), which is consistent with the Standard Model and is currently the most precise measurement of this quantity.