P-odd observables at the $\Upsilon$ peak

J. Bernabéu; F.J. Botella; O. Vives

doi:doi:10.1007/s100520050400

EPJ

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2021 Impact factor 4.991

Particles and Fields

Eur. Phys. J. C 7, 205-215
DOI 10.1007/s100529801007

P-odd observables at the $\Upsilon$ peak

J. Bernabéu¹ - F.J. Botella^1,2 - O. Vives^1,2

¹ Departament de Física Teòrica, Universitat de València, Spain
² I.F.I.C. (Centre Mixte Universitat de València-C.S.I.C.), E-46100 Burjassot, València, Spain

Received: 14 April 1998 / Revised version: 25 August 1998 / Published online: 3 December 1998

Abstract
We study the $\gamma$ -Z interference in the process $e^+ e^-\rightarrow \Upsilon \rightarrow \tau^+ \tau^-$ as a means to measure the neutral current coupling of the b-quark. The helicity amplitudes are calculated from resonant and background diagrams and the spin density matrix of the final state is discussed. The spin analyzer of the $\tau$ 's is illustrated with the decays $\pi \nu$ and $\rho \nu \rightarrow (\pi \pi) \nu$ . With $10^8 \Upsilon$ a sensitivity to g_V^b of a few per cent could be reachable.