G. Alexander et al., MEASUREMENT OF THE BRANCHING FRACTION OF THE RADIATIVE DECAY TAU(-)-]MU(-)(NU)OVER-BAR(MU)NU(TAU)GAMMA, Physics letters. Section B, 388(2), 1996, pp. 437-449
The branching ratio of the radiative tau decay tau(-) --> mu(-)<(nu)ov
er bar>(mu)nu(tau)gamma has been measured using data collected with th
e OPAL detector at LEP, The result is B(tau(-) --> mu(-)<(nu)over bar>
(mu)nu(tau)gamma) = (3.0 +/- 0.4 +/- 0.5) x 10(-3) for photon energies
above 20 MeV measured in the tau rest frame. The result is in good ag
reement with the Standard Model expectation.