STUDY OF TAU LEPTON PRODUCTION AND DECAY IN ELECTRON-POSITRON ANNIHILATIONS AT 29 GEV

KOCK KIAM GAN, Purdue University

Abstract

The reaction e('+)e('-) (--->) (tau)('+)(tau)('-) has been measured using the High Resolution Spectrometer at the e('+)e('-) storage ring PEP operated at 29 GeV. The data sample used in the analysis corresponds to an integrated luminosity of 185 pb.('-1) The angular distribution of the (tau) leptons shows a forward-backward asymmetry of -(5.2 (+OR-) 1.7 (+OR-) 0.5)%, corresponding to a product of e and (tau) axial-vector couplings g(,a)('(tau))g(,a)('e) = 0.23 (+OR-) 0.08 (+OR-) 0.03, in good agreement with the standard model of electroweak interactions. The measured cross section yields R(,(tau)(tau)) = 1.04 (+OR-) 0.02 (+OR-) 0.04, consistent with QED and giving the QED cutoff parameters of (LAMDA)(,+) > 108 GeV and (LAMDA)(,-) > 146 GeV at 95% C.L. Also presented are precise measurements of the decay branching fractions of the (tau) lepton to one and three charged particles and the first measurement of the decay branching fraction of the (tau) lepton to five charged particles. The results are B(,1) = 0.869 (+OR-) 0.002 (+OR-) 0.003, B(,3) = 0.130 (+OR-) 0.002 (+OR-) 0.003, and B(,5) = 0.0013 (+OR-) 0.0004 for the (tau) decay into one, three, and five charged particles.

Degree

Ph.D.

Subject Area

Particle physics

COinS