Resolving the Axial Mass Anomaly in neutrino Scattering

TL;DR

This paper introduces a model that accounts for the transverse enhancement in electron and neutrino quasielastic scattering, resolving the longstanding Axial Mass Anomaly by linking meson exchange currents to observed cross section discrepancies.

Contribution

The paper presents a new parametrization of the transverse response function based on electron scattering data, explaining the Axial Mass Anomaly in neutrino QE scattering.

Findings

Transverse enhancement explains the discrepancy in neutrino QE cross sections.

The model predicts improved agreement with experimental data across energies.

Meson exchange currents are key to understanding the enhancement.

Abstract

We present a parametrization of the observed enhancement in the transverse electron quasielastic (QE) response function for nucleons bound in carbon as a function of the square of the four momentum transfer (Q2) in terms of a correction to the magnetic form factors of bound nucleons. The parametrization should also be applicable to the transverse cross section in neutrino scattering. If the transverse enhancement originates from meson exchange currents (MEC), then it is theoretically expected that any enhancement in the longitudinal or axial contributions is small. We present the predictions of the "Transverse Enhancement" model (which is based on electron scattering data only) for the neutrino and anti-neutrino differential and total QE cross sections for nucleons bound in carbon. The 2Q2 dependence of the transverse enhancement is observed to resolve much of the long standing discrepancy ("Axial Mass Anomaly}) in the QE total cross sections and differential distributions between low energy and high energy neutrino experiments on nuclear targets.