Modeling neutrino-nucleus interactions for neutrino oscillation experiments

TL;DR

This paper advances the modeling of neutrino-nucleus interactions using relativistic theories, improving Monte Carlo simulations for neutrino oscillation experiments and incorporating multi-nucleon effects for better data agreement.

Contribution

It introduces a relativistic SuSAv2 model for neutrino interactions and implements multi-nucleon excitations in GENIE, enhancing simulation accuracy.

Findings

SuSAv2 model accurately predicts neutrino cross sections

Multi-nucleon excitations significantly impact cross section calculations

Model comparisons show improved agreement with T2K data

Abstract

We present our recent progress on the relativistic modeling of neutrino-nucleus reactions for their implementation in MonteCarlo event generators (GENIE, NEUT) employed in neutrino oscillation experiments. We compare charged-current neutrino and antineutrino cross sections obtained within the SuSAv2 model, which is based on the Relativistic Mean Field theory and on the analysis of the superscaling behavior exhibited by ($e,e'$) data. We also evaluate and discuss the impact of multi-nucleon excitations arising from 2p-2h states excited by the action of weak forces in a fully relativistic framework, showing for the first time their implementation in GENIE and their comparison with recent T2K data.

Full text

Current efforts in long-baseline $\nu$ experiments are aimed at improving knowledge of $\nu$ oscillations, where the development and implementation of realistic $\nu$-nucleus interaction models are essential to constrain experimental uncertainties. The current state of the art for experimental systematics is in the region of 5-10$\%$ Abe2016 and are mostly related to flux and cross section predictions (3-4$\%$). A decrease of 2-3$\%$ on these uncertainties would allow to shorten running time and experimental costs (reducing by half either the experimental exposure or the detector volume) while increasing the sensitivity to determine $\nu$ mass hierarchy or CP violation in the neutrino sector. Such a reduction of systematics will therefore represent an essential step toward understanding the matter-antimatter asymmetry in the Universe, whilst also aiding in other areas of fundamental physics, such as the analysis of supernovae explosions and the search for both sterile $\nu$ and proton decay. Accordingly, an accurate understanding of $\nu$ interaction physics is essential for current and upcoming experiments. Thus, the SuSAv2-MEC approach Megias:2016ee ; Megias:2016nu ; Ivanov14 is applied to the analysis of data from $\nu$ oscillation experiments with the aim of shedding light on the systematics arising from nuclear effects in both initial and final states. For practical purposes, the SuSAv2 model and the 2p-2h MEC contributions can be described in a simple way for different kinematics and nuclei MegiasOxygen ; MegiasMinerva ; ARFG ; nppairs ; density , translating sophisticated and demanding microscopic calculations into a relatively straightforward formalism hence easing its implementation in event generators. In Fig. 1, we show the comparison of the SuSAv2-MEC model, which is based on relativistic, microscopic calculations simomec ; megiasmec , with T2K CC0$\pi$Np data cc0pinp ; dolan for 0 protons above 500 MeV/c (left panel). The 1p1h channel corresponds to RMF-based calculations and the effect of $\pi$ emission followed by re-absorption in the nuclear medium is provided by the GENIE $\nu$-nucleus event generator genie . The 2p2h channel is generated for the first time by new implementation of the SuSAv2-MEC model within GENIE. The accurate modeling of 2p2h microscopic calculations (thick dot-dashed lines) within GENIE (solid maroon line) can be observed in the right panel, where a comparison of the full SuSAv2-MEC model with CC0$\pi$ data cc0pi is also shown. Its capability to describe data in a wide energy range and its ease to be implemented in event generators makes the SuSAv2-MEC model a promising candidate to reduce experimental systematics in current and future $\nu$ experiments.