Form factor and model dependence in neutrino-nucleus cross section predictions

Abstract

To achieve its design goals, the next generation of neutrino-oscillation accelerator experiments requires percent-level predictions of neutrino-nucleus cross sections supplemented by robust estimates of the theoretical uncertainties involved. The latter arise from both approximations in solving the nuclear many-body problem and in the determination of the single-and few-nucleon quantities taken as input by many-body methods. To quantify both types of uncertainty, we compute flux-averaged double-differential cross sections using the Green's function Monte Carlo and spectral function methods as well as different parameterizations of the nucleon axial form factors based on either deuterium bubble-chamber data or lattice quantum chromodynamics calculations. The cross-section results are compared with available experimental data from the MiniBooNE and T2K collaborations. We also discuss the uncertainties associated with N → ∆ transition form factors that enter the two-body current operator. We quantify the relations between neutrino-nucleus cross section and nucleon form factor uncertainties. These relations enable us to determine the form factor precision targets required to achieve a given cross-section precision.

Lepton–Nucleus Interactions within Microscopic Approaches

“…In Ref. [37] a study of the dependence of the neutrino-nucleus cross section results from the axial form factor adopted in the one-body current operator has been carried out using the GFMC and the SF approaches and a tension between the results obtained for the LQCD and phenomenological form factors has been observed. The results of Ref.…”

“…The results of Ref. [37] indicate that while significant progress has been made in the determination of the axial and vector form factors entering in the one-body current operator, more work will be required in the future for the determination of the form factors entering the two-body currents, particularly for those contributions with ∆ degrees of freedom.…”

“…The impact of these tensions in the Q 2 dependence of the axial form factor on neutrino-nucleus cross section predictions has been discussed in Refs. [73,74] and recently in [37,75]. For the CC processes, we report the nonrelativistic reduction of the charge and axial current operators [77] (for brevity, we neglect order 1/m 2 N terms)…”

“…Recently, the authors of Ref. [37] computed flux-folded differential cross sections for MiniBooNE and T2K experiments [131,132] using the QMC spectral function outlined above. Under control systematics, the calculation of the two-body contribution is required for disentangling the effect of the axial form factor.…”

“…In contrast with the GFMC, the SF approach can access exclusive channels and larger nuclei. However, while based on a similar treatment of the initial target state, factorizing the final state involves additional approximations, which are only valid at large momentum transfer and whose validity can be tested against comparisons with GFMC calculations [36,37].…”