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Register a new userQuasielastic axial-vector mass from experiments on neutrino-nucleus scattering
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We analyze available experimental data on the total and differential charged-current cross sections for quasielastic neutrino and antineutrino scattering off nucleons, measured with a variety of nuclear targets in the accelerator experiments at ANL, BNL, FNAL, CERN, and IHEP, dating from the end of sixties to the present day. The data are used to adjust the poorly known value of the axial-vector mass of the nucleon.
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The axial form factor plays a crucial role in quasielastic neutrino-nucleus scattering, but the error of the theoretical cross section due to uncertainties of $G_A$ remains to be established. Reversely, the extraction of $G_A$ from the neutrino nucleus cross section suffers from large systematic errors due to nuclear model dependencies, while the use of single parameter dipole fits underestimates the errors and prevents an identification of the relevant kinematics for this determination. We propose to use a generalized axial-vector-meson-dominance (AVMD) in conjunction with large-$N_c$ and high energy QCD constrains to model the nucleon axial form factor, as well as the half width rule as an a priori uncertainty estimate. The minimal hadronic ansatz comprises the sum of two monopoles corresponding to the lightest axial-vector mesons being coupled to the axial current. The parameters of the resulting axial form factor are the masses and widths of the two axial mesons as obtained from the averaged PDG values. By applying the half width rule in a Monte Carlo simulation, a distribution of theoretical predictions can then be generated for the neutrino-nucleus quasielastic cross section. We test the model by applying it to the $( u_mu,mu)$ quasielastic cross section from $^{12}$C for the kinematics of the MiniBooNE experiment. The resulting predictions have no free parameters. We find that the relativistic Fermi gas model globally reproduces the experimental data, giving $chi^2/ # bins = 0.81$. A $Q^2$-dependent error analysis of the neutrino data shows that the uncertainties in the axial form factor $G_A(Q^2)$ are comparable to the ones induced by the a priori half width rule. We identify the most sensitive region to be in the range $0.2 lesssim Q^2 lesssim 0.6 ,{rm GeV}^2$.
We study the scattering of neutrinos on polarized and unpolarized free nucleons, and also the polarization of recoil particles in these scatters. In contrast to electromagnetic processes, the parity-violating weak interaction gives rise to large spin asymmetries at leading order. Future polarization measurements could provide independent access to the proton axial structure and allow the first extraction of the pseudoscalar form factor from neutrino data without the conventional partially conserved axial current (PCAC) ansatz and assumptions about the pion-pole dominance. The pseudoscalar form factor can be accessed with precise measurements with muon (anti)neutrinos of a few hundreds $mathrm{MeV}$ of energy or with tau (anti)neutrinos. The axial form factor can be extracted from scattering measurements using accelerator neutrinos of all energies.
We analyse available experimental data on the total charged-current neutrino-nucleon and antineutrino-nucleon cross sections for quasielastic scattering and single-pion neutrinoproduction. Published results from the relevant experiments at ANL, BNL, FNAL, CERN, and IHEP are included dating from the end of sixties to the present day, covering muon neutrino and antineutrino beams on a variety of nuclear targets, with energies from the thresholds to about 350 GeV. The data are used to adjust the poorly known values of the axial masses.
High precision studies of Beyond-Standard-Model physics through accelerator-based neutrino oscillation experiments require a very accurate description of neutrino-nucleus cross sections in a broad energy region, going from quasielastic scattering up to deep inelastic scattering. In this work we focus on the following processes: quasielastic scattering, two-particle-two-hole excitations, and the excitation of the first (Delta) and second (Roper) resonances of the nucleon. The nuclear model is fully relativistic and includes both one- and two-body currents. We compare our results with recent T2K and MicroBooNE data on carbon and argon targets, and present predictions for DUNE kinematics.
The charged-current double differential neutrino cross section, measured by the MiniBooNE Collaboration, has been analyzed using a microscopical model that accounts for, among other nuclear effects, long range nuclear (RPA) correlations and multinucleon scattering. We find that MiniBooNE data are fully compatible with the world average of the nucleon axial mass in contrast with several previous analyses which have suggested an anomalously large value. We also discuss the reliability of the algorithm used to estimate the neutrino energy.
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