Weak neutral current axial form factor using left(overline{nu}right)nu -nucleon scattering and lattice QCD inputs

Abstract

We present a determination of the neutral current weak axial charge {G}_A^Z(0)=-0.654{(3)}_{mathrm{stat}}{(5)}_{mathrm{sys}} using the strange quark axial charge {G}_A^s(0) calculated with lattice QCD. We then perform a phenomenological analysis, where we combine the strange quark electromagnetic form factor from lattice QCD with (anti)neutrino-nucleon scattering differential cross section from MiniBooNE experiments in a momentum transfer region 0.24 ≲ Q2 ≲ 0.71 GeV2 to determine the neutral current weak axial form factor {G}_A^Zleft({Q}^2right) in the range of 0 ≲ Q2 ≤ 1 GeV2. This yields a phenomenological value of {G}_A^Z(0) = −0.687(89)stat(40)sys. The value of {G}_A^Z(0) constrained by the lattice QCD calculation of {G}_A^s(0) , when compared to its phenomenological determination, provides a significant improvement in precision and accuracy and can be used to provide a constraint on the fit to {G}_A^Zleft({Q}^2right) for Q2> 0. This constrained fit leads to an unambiguous determination of (anti)neutrino-nucleon neutral current elastic scattering differential cross section near Q2 = 0 and can play an important role in numerically isolating nuclear effects in this region. We show a consistent description of {G}_A^Zleft({Q}^2right) obtained from the (anti)neutrino-nucleon scattering cross section data requires a nonzero contribution of the strange quark electromagnetic form factor. We demonstrate the robustness of our analysis by providing a post-diction of the BNL E734 experimental data.