M. Kalelkar | Searcharxiv

arXiv2000

Light Quark Fragmentation in Polarized Z0 Decays at SLD

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- --> Z0 --> q-q(bar). 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 q-q(bar) axis. The other topic is the first direct measurement of A_s, the parity-violating coupling of the Z0 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.

hep-ex↗

arXiv1998

Identified Hadron Production and Light Quark Fragmentation in Z0 Decays

We have measured the differential cross sections for the production of $π^{+}$, $K^{+}$, $K^{0}$, $K^{*0}$, $ϕ$, p, $Λ$ and their corresponding antiparticles in separate samples of flavor-tagged $Z^{0}\to$ light-flavor ($u\bar{u}$, $d\bar{d}$, or $s\bar{s}$), $Z^{0}\to c\bar{c}$ and $Z^{0}\to b\bar{b}$ events. Clear flavor dependences are observed, and the results are compared with the predictions of three fragmentation models. We have also performed a 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. Our preliminary result is $A_{s}$ = $0.82\pm 0.10(stat.)\pm 0.07(syst.)$.

hep-ex↗