Weak quasielastic hyperon production leading to pions in the antineutrino-nucleus reactions

TL;DR

This paper reviews weak quasielastic hyperon production in antineutrino-nucleus reactions, highlighting its role in pion production and its potential to test fundamental symmetries and form factors in the strangeness sector.

Contribution

It provides new insights into hyperon polarization and cross sections, and their dependence on energy and momentum transfer, for various nuclear targets relevant to current neutrino experiments.

Findings

Hyperon polarization components are sensitive to second class currents.

Hyperon decay significantly contributes to pion production in sub-GeV energies.

Cross sections and polarization depend on energy and Q^2, aiding form factor determination.

Abstract

In this review, we have studied the quasielastic production cross sections and polarization components of $\Lambda$, $\Sigma^0$ and $\Sigma^-$ hyperons induced by the weak charged currents in the antineutrino reactions on the nucleon and the nuclear targets like $^{12}$C, $^{16}$O, $^{40}$Ar and $^{208}$Pb. It is shown that the energy and the $Q^2$ dependence of the cross sections and the various polarization components can be effectively used to determine the axial vector transition form factors in the strangeness sector and test the validity of various symmetry properties of the weak hadronic currents like G-invariance, T-invariance and SU(3) symmetry. In particular, the energy and the $Q^2$ dependence of the polarization components of the hyperons is found to be sensitive enough to determine the presence of the second class current with or without T-invariance. These hyperons decay dominantly into pions giving an additional contribution to the weak pion production induced by the antineutrinos. This contribution is shown to be quantitatively significant as compared to the pion production by the $\Delta$ excitation in the nuclear targets in the sub-GeV energy region relevant for the $\bar{\nu}_\mu$ cross section measurements in the oscillation experiments. We have also included a few new results, based on our earlier works, which are in the kinematic region of the present and future (anti)neutrino experiments being done with the accelerator (anti)neutrinos at T2K, MicroBooNE, MiniBooNE, NO$\nu$A, MINER$\nu$A and DUNE, as well as for the atmospheric (anti)neutrino experiments in this energy region.