Measurement of $A_c$ with charmed mesons at SLD

TL;DR

This paper reports a direct measurement of the parity-violation parameter A_c using 550,000 Z^0 decays at SLD, employing charm meson reconstruction and soft-pion tagging methods, resulting in A_c = 0.688 with statistical and systematic uncertainties.

Contribution

It introduces a combined approach using exclusive charm meson reconstruction and inclusive soft-pion tagging to measure A_c at SLD.

Findings

Measured A_c = 0.688 ± 0.035(stat.) ± 0.025(sys.)

Used 550,000 Z^0 decays and polarized electron beam

Demonstrated effective charm tagging methods

Abstract

We present a direct measurement of the parity-violation parameter A_c. The measurement is based on 550k Z^0 decays collected by the SLD detector. The mean electron-beam polarization is |P_e| = 73 %. The tagging of c-quark events was performed using two methods: The exclusive reconstruction of D^*+, D^+, and D^0 mesons, and the inclusive P_T spectrum of soft-pions (pi_s) in the decay of D^*+ -> D^0 pi_s^+. The results of these two methods are combined to give A_c = 0.688 +- 0.035(stat.) +- 0.025(sys.) (preliminary).