Exploring Nuclear Aspects of Neutrino Interactions in Neutrino Oscillation Experiments

Project Information

NeutrinoNucleai

Grant agreement ID: 101078772

DOI

10.3030/101078772

EC signature date 1 December 2022

Start date 1 January 2023

End date 31 December 2027

Funded under

• European Research Council (ERC)

Total cost

€ 1 500 000,00

EU contribution

€ 1 500 000,00

Coordinated by

TEL AVIV UNIVERSITY
Israel

Periodic Reporting for period 1 - NeutrinoNucleai (Exploring Nuclear Aspects of Neutrino Interactions in Neutrino Oscillation Experiments)

Reporting period: 2023-01-01 to 2025-06-30

Summary of the context and overall objectives of the project

The ability of current and next generation accelerator based neutrino oscillation measurements to reach their desired sensitivity and provide new insight into the nature of our Universe, requires a high-level of understanding of the neutrino-nucleus interactions. These include precise estimation of the relevant cross sections and the reconstruction of the incident neutrino energy from the measured final state particles. Incomplete understanding of these interactions can skew the reconstructed neutrino spectrum and thereby bias the extraction of fundamental oscillation parameters and searches for new physics.
This proposal exploit the similarity of electron- and neutrino-nucleus interactions. It leverages wide phase-space exclusive electron scattering data with known beam energies as well as neutrino scattering data in the same energy region and on similar nuclear targets, to test energy reconstruction methods and interaction models.
The ERC NeutrinoNuclei project will deliver well constrained simulation environment and uncertainties of the neutrino-nuclei interaction, to meet the requirements of future high-precision experiments.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

During this reporting period, significant progress has been made in advancing our understanding of the neutrino interaction with the nuclei. The focus has been on achieving key milestones in the various working packages: Electron scattering data, neutrino scattering data, and Model improvements. Preliminary work has started on the fourth working package: Model tuning. This section details the research findings, technological innovations, and overall progress toward the project's goals.

Electron scattering: A local team of a postdoc, two graduate students and two summer students have made significant progress and their work is nearing publication. Measurements from the CLAS and CLAS12 experiments are already presented in leading conferences: A new inclusive analysis of electron scattering on carbon and argon shows for the first time how problematic the current approach of scaling predictions by the atomic number is. Three semi-exclusive analyses are in the pipe-line: The first being electron scattering with 1 proton and 1 pion is in final stages shading light on the resonance interaction process. The DUNE experiment is the first accelerator-based neutrino oscillation experiment to feature the highest-energy incoming neutrino flux with a broad energy distribution. Given these conditions, numerous neutrino interactions are expected to occur through the resonance process, leading to this specific final state. As a result, this analysis will be crucial for the success of DUNE. Another analysis with only 1 pion in the final state will be of great impact to Cherenkov-based neutirno experiments. A first of a kind analysis of electron scattering with two nucleons (either 2 protons or 1 proton and 1 neutron) is also in progressed stages. The analyser of the last spent a 6 weeks at Jefferson Lab where the experiment is located and worked with local experts to improve the efficiency of neutron detection, crucial for his and others’ analyses.

Neutrino scattering: As part of the MicroBooNE collaboration, we have focused on the neutrino scattering resulting with 1 muon and 1 proton in the final state. Our group member has improved the efficiency to identify relevant vertices. Based on our previous publication, we have suggested and now executing an innovating approach for an oscillation measurement. We choose events with high probability of being quasi elastic as the model of this process is familiar and its uncertainty is low and trustable. Though reducing the number of events increases the statistical uncertainties, the sensitivity is expected to increase as the cross section uncertainties are smaller.
We have had a great progress in the mu4nu initiative, aiming to trigger on muon interaction inside neutirno experiment by identifying multiple prong topologies. In addition our group took a leading part in a pioneering analysis, aiming to use future neutrino scattering data in an innovative way: A measurements of neutrino interactions at different off-axis angles using the DUNE-PRISM detector can be exploited to create narrow virtual fluxes (less than 100 MeV wide).

Models: As planned , our group has made a significant contributions to the electron mode of event generator:
In order to compare data and generated events, radiative effects need to be included in the event generators. We implemented a universal radiative corrections program that can be used with all reaction mechanisms and any eA event generator. This achievement has been recently published.
The second contribution deals with in the Super-Scaling Approach (SuSA) in the GENIE event generator. This approach estimates the inclusive cross section by scaling inclusive electron scattering data on specific nuclei. SuSA’s implementation in the electron mode of GENIE was found to have a problem, simulating only 1n1p events out of the 2p2h finale states (namely, no 2n nor 2p events were generated). A team member has identified and fixed this problem. This fix is now public in the new version of GENIE.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

Below are the key scientific publications and outputs of the NeutrinoNuclei project to date. I have included only those that have already resulted in publications or publicly available results, as their impact can be assessed
1. The universal implementation of radiative effects in neutrino event generator has already made public (Computer Physics Communications 310(7886)). Its universality allows its implementation in various event generators, and it inclusiveness (ability to handle all interaction mechanisms and final states) makes it applicable to many analyses.
2. The recently extracted inclusive electron scattering cross section on carbon and argon was already made pubic in various conferences and in progressed stages of being officially published. This measurement provides unprecedented angular coverage and offers the first detailed insight into electron scattering on argon, the target material in LArTPC experiments—the next-generation technology for the DUNE neutrino oscillation experiment.
3. Initial results from the electron scattering cross section with 1 proton and 1 pion in the final state has been presented at conferences and is making a significant impact. The data reveals discrepancies with existing models in the resonance region, highlighting the need for tuning the parameters in the nuclear the form factors. In addition, the difference between the positive and negative pion cases highlight the importance of tuning the Final state interaction models used.
4. Utilizing Transverse Kinematic Imbalance Variables for neutrino oscillation analyses. This idea described above resulted with a new analysis being conducted by the MicroBooNE experiment.

While each individual achievement may not constitute a breakthrough on its own, the combined impact of our work is significantly advancing the field beyond the current state-of-the-art. Our contributions, ranging from novel data analysis techniques to model parameters tuning, are collectively improving our estimation of neutrino scattering cross section and their uncertainties, which has a direct impact on the sensitivity and reliability of future neutrino oscillation measurements.