Nuclear transparency in Monte Carlo neutrino event generators

Abstract

Hadron cascade model is an essential part of Monte Carlo neutrino event generators that governs final state interactions of knocked-out nucleons and produced pions. It is shown that such model enriched with physically motivated modifications of nucleon-nucleon cross section and incorporation of nuclear correlation effects is able to reproduce experimental nuclear transparency data. Uncertainty of nucleon final state interactions effects is estimated and applied to recent neutrino-nucleus cross section measurements including an outgoing proton in the experimental signal. Conclusions are drawn on a perspective of identification of events originating from two-body current mechanism.

A quantum Monte Carlo based approach to intranuclear cascades

“…An alternative way to include correlation effects in INC models, based on two-body density distributions, has been recently proposed by the NuWro collaboration and leads to a larger enhancement of the nuclear transparency than we find [49]. This difference can partly be ascribed to correlation terms between two spectator nucleons [79] that are automatically incorporated in our QMC configurations, but cannot be modeled by the twobody correlation functions alone.…”

“…As a consequence, they mildly affect our calculations of p-carbon scattering and carbon transparency. The results presented for the latter quantity by the NuWro collaboration indicate a larger importance of nuclear correlations, whose implementation is based on the two-body density distributions [49].…”

“…Despite some differences in technical aspects and degree of sophistication, all the above INC models use as input elementary cross sections and mean-field properties of nuclei, such as single-nucleon densities. A notable exception is NuWro, which has recently been ex-tended to incorporate effective nucleon-nucleon correlations [49].…”

Data-based two-body current contribution to the neutrino-nucleus cross section

“…The data analysis does not depend on uncertain predictions for the hadrons in the final state. The available theoretical models for the 2p2h contribution give predictions for the final-state lepton only and modeling final-state hadrons is based on approximations [5] and nucleon final-state interactions effects [24].…”

Data based two-body current contribution to neutrino-nucleus cross section

“…The data analysis does not depend on uncertain predictions for the hadrons in the final state. The available theoretical models for the 2p2h contribution give predictions for the final state lepton only and modeling final state hadrons is based on approximations [6] and nucleon final state interactions effects [24].…”