$C_5^A$ axial form factor from bubble chamber experiments

TL;DR

This paper reanalyzes experimental data on weak pion production to accurately determine the axial form factor $C_5^A$, accounting for nuclear effects and uncertainties, with implications for neutrino oscillation experiments.

Contribution

It provides a refined extraction of the $C_5^A$ axial form factor from bubble chamber data, considering nuclear effects and uncertainties, improving the understanding of weak pion production.

Findings

$C_5^A(0)=1.19\, ext{±}\,0.08$

$M_A=0.94\, ext{±}\,0.03$ GeV

Good agreement between Argonne and Brookhaven data

Abstract

A careful reanalysis of both Argonne National Laboratory and Brookhaven National Laboratory data for weak single pion production is done. We consider deuteron nuclear effects and normalization (flux) uncertainties in both experiments. We demonstrate that these two sets of data are in good agreement. For the dipole parametrization of $C_5^A(Q^2)$, we obtain $C_5^A(0)=1.19\pm 0.08$, $M_A=0.94\pm 0.03$ GeV. As an application we present the discussion of the uncertainty of the neutral current 1$\pi^0$ production cross section, important for the T2K neutrino oscillation experiment.