Coherent effects of a weak neutral current

TLDR

If a weak neutral current exists, elastic neutrino–nucleus scattering should exhibit a sharp coherent forward peak, with cross sections nearly energy‑independent, making low energies (~100 MeV) suitable for observation. Experiments observing this peak can provide important information on the isospin structure of the neutral current. The experiments are very difficult, though estimated cross sections (~10⁻³⁸ cm² on carbon) are favorable, and quasi‑coherent nuclear excitation processes offer possible tests of weak neutral current conservation. Strong coherent effects at very low energies imply that nuclear elastic scattering may significantly inhibit neutrino cooling during stellar collapse and in neutron stars.

Abstract

If there is a weak neutral current, then the elastic scattering process $\ensuremath{\nu}+A\ensuremath{\rightarrow}\ensuremath{\nu}+A$ should have a sharp coherent forward peak just as $e+A\ensuremath{\rightarrow}e+A$ does. Experiments to observe this peak can give important information on the isospin structure of the neutral current. The experiments are very difficult, although the estimated cross sections (about ${10}^{\ensuremath{-}38}$ ${\mathrm{cm}}^{2}$ on carbon) are favorable. The coherent cross sections (in contrast to incoherent) are almost energy-independent. Therefore, energies as low as 100 MeV may be suitable. Quasi-coherent nuclear excitation processes $\ensuremath{\nu}+A\ensuremath{\rightarrow}\ensuremath{\nu}+{A}^{*}$ provide possible tests of the conservation of the weak neutral current. Because of strong coherent effects at very low energies, the nuclear elastic scattering process may be important in inhibiting cooling by neutrino emission in stellar collapse and neutron stars.