Abstract
A joint fit to neutrino-nucleon scattering and pion electroproduction data is performed to evaluate the nucleon axial form factor in the two-component model consisting of a three-quark intrinsic structure surrounded by a meson cloud. Further constrains on the model are obtained by re-evaluating the electromagnetic form factor using electron scattering data. The results of the axial form factor show sizable differences with respect to the widely used dipole model. The impact of such changes on the Charged-Current Quasi-Elastic neutrino-nucleus cross-section is evaluated in the SuSAv2 nuclear model, based on the Relativistic Mean Field and including the contribution of two-body currents. How the different parametrizations of the axial form factor affect the cross-section prediction is assessed in full details and comparisons to recent T2K and MINERvA data are presented.
Highlights
The accurate knowledge of the nucleon’s form factors and a good control of nuclear effects in neutrino-nucleus scattering in the GeV region are mandatory requirements for the analysis and interpretation of ongoing and planned neutrino oscillation experiments [1,2,3,4], which aim at measuring neutrino properties with unprecedented precision and search for charge conjugation parity violation in the leptonic sector.While the weak vector form factors of the nucleon are related to the electromagnetic ones through conservation of vector current (CVC) and are relatively well under control in the kinematical region of interest for these experiments, an important source of uncertainty arises from poor knowledge of the axial form factor GA
II we describe the main features of the two-component model for the axial form factor of the nucleon (II A), we re-evaluate the electromagnetic form factors in such model (II B), and we perform the first evaluation of two-component model axial form factor with a joint fit to neutrino scattering and pion electroproduction data (II C)
While the relativistic mean field (RMF) approach works properly at low to intermediate values of the momentum transfer q, where the effects linked to the treatment of the final-state interactions (FSI) are significant, it fails at higher q due to the strong energy-independent scalar and vector RMF potentials, whose effects should instead become less important with increasing momentum transfer
Summary
The accurate knowledge of the nucleon’s form factors and a good control of nuclear effects in neutrino-nucleus scattering in the GeV region are mandatory requirements for the analysis and interpretation of ongoing and planned neutrino oscillation experiments [1,2,3,4], which aim at measuring neutrino properties with unprecedented precision and search for charge conjugation parity violation in the leptonic sector. While the weak vector form factors of the nucleon are related to the electromagnetic ones through conservation of vector current (CVC) and are relatively well under control in the kinematical region of interest for these experiments, an important source of uncertainty arises from poor knowledge of the axial form factor GA This occurrence gave rise to the so-called MA puzzle when the first neutrino-carbon cross sections were published by the MiniBooNE Collaboration [5] and found to be largely underestimated by the theoretical prediction, unless a value of the axial cutoff MA = 1.35 GeV was used in place of the standard value MA 1 GeV.
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