Probe of the hadronic neutral current by final-proton polarization

Abstract

A systematic phenomenological analysis of the final-proton polarization in the neutral-current reaction ${\ensuremath{\nu}}_{\ensuremath{\mu}}({\overline{\ensuremath{\nu}}}_{\ensuremath{\mu}})p\ensuremath{\rightarrow}{\ensuremath{\nu}}_{\ensuremath{\mu}}({\overline{\ensuremath{\nu}}}_{\ensuremath{\mu}})p$ is given. It is shown that a measurement of the transverse polarization of the final proton could effectively discriminate between competing gauge-theory models (two classes of models predict large polarizations of opposite sign) and that it could also distinguish $V$, $A$ neutral-current interactions from $S$, $P$, $T$. Longitudinal and (time-reversal-violating) orthogonal polarizations are also considered, as are the polarizations expected in quasielastic scattering.