Neutrino-nucleus interactions lie at a compelling intersection between nuclear and particle physics. Cross sections describing these interactions impart a leading systematic uncertainty in the evaluation of neutrino oscillation parameters, key measurement outputs of near detectors empowering the Long-Baseline era soon to be upon us. While incredibly useful, the adoption of Monte Carlo neutrino event generators such as GENIE, GiBUU, NuWro, and NEUT by particle physics experiments can only roughly ascertain the uncertainties in these cross sections via predominately reweighting schemes. Microscopic approaches to neutrino-nucleus interactions are just beginning to be implemented in these generators, and they can be further refined using input from future experiments and lattice QCD. Quantitatively understanding how uncertainties in the inputs and approximations of nuclear theories propagate through event generators is critical for quantifying cross-section uncertainties and assessing the most important steps for reducing them. Robust systematic error quantification and connections between the Standard Model and neutrino event generator predictions are essential both for accurately determining neutrino oscillation parameters and for enabling the discovery of new physics at forthcoming neutrino experiments.
Achieving a comprehensive description of neutrino-nucleus cross sections in the broad range of energies relevant for oscillation experiments is a formidable nuclear theory challenge which requires the introduction of controlled approximation within nuclear many-body models. For this reason, a precise quantification of the theoretical uncertainty of the cross-section calculation has not been achieved so far. To fill this gap, event generator specialists and experimentalists resort to approximate methods to derive the uncertainties they require to claim measurements of particular calibers. This approximate method also leaves much to be desired if and when BSM physics is potentially measured for the first time.
The scope of this workshop is to bring together nuclear and particle theorists and define a strategy to better ascertain theory-related uncertainties. Assessing how nuclear EFTs can be extended to account for processes characterized by momentum and energy scales larger than the pion mass and what the associated uncertainties of great relevance are for the nuclear physics community. Fostering detailed discussions about uncertainty quantification in neutrino-nucleus scattering theory, including comparisons to electron scattering experiments as pioneered by the $e4\nu$ initiative, will strengthen the self-consistent application of precision nuclear theory to neutrino experiments and more broadly.
Image credit: Symmetry Magazine, "The Hidden Neutrino"