Tau leptonic branching ratios

A sample of 62249 τ-pair events is selected from data taken with the ALEPH detector in 1991, 1992 and 1993. The measurement of the branching fractions for τ decays into electrons and muons is presented with emphasis on the study of systematic effects from selection, particle identification and decay classification. The results obtained are: Be = 17.79±0.12(stat)±0.06(syst)(%) and Bμ= 17.31±0.11(stat)±0.05(syst)(%). Combined with the most recent ALEPH determination of the τ lifetime, these results provide a relative measurement of the leptonic couplings in the weak charged current for transverse W bosons:

{cal G}_{ώ}/{cal G}_{e}=1.0002pm 0.0051

and

{cal G}_{∢u}/{cal G}_{u}=0.9943pm 0.0065

.

electron positron: colliding beams
colliding beams: electron positron
electron positron: annihilation
annihilation: electron positron
tau: electroproduction
electroproduction: tau
tau: pair production
pair production: tau
tau: leptonic decay
leptonic decay: tau

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