New evaluation of the axial nucleon form factor from electron- and neutrino-scattering data and impact on neutrino-nucleus cross sections

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 reevaluating 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 crosssection prediction is assessed in full details and comparisons to recent T2K and MINERvA data are presented.

LSND constraints on the Higgs portal

“…4. We utilize a dipole form for the pion-nucleon form factor ∼1=ð1 þ Q 2 =m 2 A Þ 2 , where m A ∼ 1 GeV is the axial mass [72,73], and similarly the proton electromagnetic form factor F 1 ðQ 2 Þ ∼ 1=ð1 þ Q 2 =ð0.71 GeVÞ 2 Þ 2 . The contribution from one-pion exchange is significant in a narrow energy range, and it is known that additional processes, such as twopion exchange, become important for beam momenta above 600-700 MeV [74,75].…”

Simultaneous measurement of the muon neutrino charged-current cross section on oxygen and carbon without pions in the final state at T2K

“…CCQE, also often referred to as "1p1h" (one-particle one-hole), is the dominant reaction mode at T2K neutrino energies (peaked at 600 MeV) and therefore it is the interaction which is most important to characterize for T2K's neutrino oscillation measurements. While CCQE interactions with free nucleons are relatively simple to model [12], the situation becomes much more complex when the struck nucleon is bound inside a nucleus, that has an unknown initial momentum and binding energy. Moreover, the final state interactions (FSI) of outgoing hadrons inside the nuclear medium make CCQE interactions practically indistinguishable from mesonproduction interactions with subsequent meson-absorption FSI.…”

Neutrino-nucleus scattering in the SuSA model

“…This implies important phase-space restrictions for large energy and momentum transfer to the nuclear target and makes the available phase space not so different from the T2K one, as shown in Ref. [75].…”