W radiative decays and the determination of magnetic dipole and electric quadrupole moments of the W.

Abstract

The magnetic dipole moment of the {ital W} boson is given by {mu}={ital e}(1+{kappa}+{lambda})/2{ital M}{sub {ital W}} and its electric quadrupole moment is given by {ital Q}={minus}{ital e}({kappa}{minus}{lambda})/{ital M}{sub {ital W}}{sup 2}. A nonstandard magnetic dipole moment and a nonstandard electric quadrupole moment lead to different differential decay distributions in the radiative decays of {ital W}{sup {plus minus}}, {ital W}{sup {minus}}{r arrow}{ital e}{bar {nu}}{gamma} and {ital W}{sup {minus}}{r arrow}{ital d{bar u}}{gamma}. While hard photons are characteristic signatures of {kappa}{ne}1 there is no such explicit signal for {lambda}{ne}0. We present a technique for the determination of the values of {kappa} and {lambda} by measuring the total number of events in two regions of phase space. This experiment could be done at the CERN {ital e}{sup +}{ital e{minus}} collider LEP II, where a clean source of {ital W} bosons will be available.