Lorentz structure of weak current in ν interactions and inverse muon decay

Abstract

Neutrino interactions uniquely convey the Lorentz structure of weak current. Two studies that probe this structure are reviewed: structure functions from ν μ − and ν μ − induced charged current events; and the inverse muon decay process, ν μ +e −→ μ −+ ν e. In the first study, the relative absence of ν μ -induced charged current events with respect to ν μ -induced events at large z (> 0.45) and large y (> 0.70) (investigated by CDHS and CCFR) restricts |η| 2 = |g R/g L| 2 < 0.0015 with 90 % CL (CCFR). Within the framework of left-right symmetric models, this measurement imposes a limit upon the mixing angle of the left and right handed bosons. Unlike the limits imposed by the μ-decay and the nuclear β-decay experiments, the present limit is valid irrespective of the mass of the right handed neutrino. In the second study, recent high statistics measurements of inverse muon decay by CCFR and CHARM II yield a total cross section, σ( ν μ +e −→ μ −+ ν e) = (17.3±0.72(stat)±0.39(syst)]E ν 10 −42 cm 2/GeV. This restricts the scalar coupling of the muon | g LL S | < 0.25 with 90% CL.