Measurement of the quasi-elastic axial vector mass in neutrino-oxygen interactions

TL;DR

This paper measures the axial vector mass in neutrino-oxygen quasi-elastic interactions using a large dataset and a relativistic Fermi gas model, providing a precise value that informs neutrino interaction models.

Contribution

It presents a new measurement of the axial vector mass M_A in neutrino-oxygen interactions using experimental data and updated form factors, with detailed analysis of nuclear effects.

Findings

Measured M_A as 1.20 ± 0.12 GeV

Analyzed over 12,000 neutrino events

Included updated vector form factors

Abstract

The weak nucleon axial-vector form factor for quasi-elastic interactions is determined using neutrino interaction data from the K2K Scintillating Fiber detector in the neutrino beam at KEK. More than 12,000 events are analyzed, of which half are charged-current quasi-elastic interactions nu-mu n to mu- p occurring primarily in oxygen nuclei. We use a relativistic Fermi gas model for oxygen and assume the form factor is approximately a dipole with one parameter, the axial vector mass M_A, and fit to the shape of the distribution of the square of the momentum transfer from the nucleon to the nucleus. Our best fit result for M_A = 1.20 \pm 0.12 GeV. Furthermore, this analysis includes updated vector form factors from recent electron scattering experiments and a discussion of the effects of the nucleon momentum on the shape of the fitted distributions.