Axial and pseudoscalar form factors from charged current quasielastic neutrino-nucleon scattering

TL;DR

This paper explores how neutrino scattering experiments can directly measure the axial and pseudoscalar form factors of the nucleon, providing new insights into its internal structure without relying on traditional assumptions.

Contribution

It proposes a method to extract the pseudoscalar form factor from neutrino scattering data independently of the PCAC hypothesis and pion-pole dominance assumptions.

Findings

Large spin asymmetries due to parity violation can be observed.

Neutrino scattering can directly access the pseudoscalar form factor.

Axial form factor can be measured across various neutrino energies.

Abstract

We study the scattering of neutrinos on polarized and unpolarized free nucleons, and also the polarization of recoil particles in these scatters. In contrast to electromagnetic processes, the parity-violating weak interaction gives rise to large spin asymmetries at leading order. Future polarization measurements could provide independent access to the proton axial structure and allow the first extraction of the pseudoscalar form factor from neutrino data without the conventional partially conserved axial current (PCAC) ansatz and assumptions about the pion-pole dominance. The pseudoscalar form factor can be accessed with precise measurements with muon (anti)neutrinos of a few hundreds $\mathrm{MeV}$ of energy or with tau (anti)neutrinos. The axial form factor can be extracted from scattering measurements using accelerator neutrinos of all energies.