ISSN - 09205632, Nuclear Physics B - Proceedings Supplements, 2007, vol. 169, p. 125-131
New precise determination of the τ lepton mass at KEDR detector
The status of the experiment on the precise τ lepton mass measurement running at the VEPP-4M collider with the KEDR detector is reported. The mass value is evaluated from the τ+ τ- cross section behaviour around the production threshold. The preliminary result based on 6.7 pb-1 of data is mτ = 1776.80-0.23 +0.25 ± 0.15 MeV. Using 0.8 pb-1 of data collected at the ψ′ peak the preliminary result is also obtained: Γe e ṡ Bτ τ (ψ′) = 7.2 ± 2.1 eV. © 2007 Elsevier B.V. All rights reserved.