Measurement of the tau -lepton mass.
نویسندگان
چکیده
Beijing The mass of the ~ lepton has been measured at the Beijing Electron Positron Collider using the Beijing Spectrometer. A search near threshold for e+e-~ ~+~-was performed. Candidate events were identified by requiring that one T decay via ~ ~ ev>, and the other via 74 pvti. The mass value, obtained from a fit to the energy dependence of the T+7-cross section, is m, = 1776.9~~:~ + 0.2 MeV. It has recently been the focus of much attention that the current [2] (RPP92) averages of the ~ electronic branching ratio B; = (17.93 + 0.26)~0, lifetime t,= (3.05+0.06) x 10-13 s, and mass m, = 1784.1~~:~ MeV are inconsistent at the 2.4 a level with the lepton universality implied by the SU(2) x U(l) gauge symmetry of the Standard Model. Within this model leptonic decay rates are ziven bv /31 t (1) where mL is the 'mass of the parent lepton L, GL is the Fermi weak-coupling constant and the correction factor FCO,is given by t Fcor = f(~) x Fw x FRAD, (2) with f(z) = 1 –8x +8z3 –X4 – 12z21nx,
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عنوان ژورنال:
- Physical review. D, Particles and fields
دوره 47 9 شماره
صفحات -
تاریخ انتشار 1993