Hadronic Physics for Neutrino-Nucleon Interactions

Indiana University, Bloomington IN

Investigators

Abstract

Modern nuclear and particle physics are concerned with understanding the fundamental parameters and symmetries of nature. Quarks are particles that interact via the strong force, which binds them together in an atomic nucleus. Leptons do not feel this force; the most familiar example of a lepton is the electron that binds to the nucleus by the electromagnetic interaction. A more exotic lepton is the neutrino, which has no electric charge and interacts only weakly.  Yet, this elusive particle is proving to be a crucial link in our search for new physics phenomena. Exquisite experimental measurements over the last two decades revealed that the neutrinos have small but nonzero masses. Today, the field of neutrino physics enters a precision era, with accelerator-based neutrino oscillation experiments taking center stage in the experimental program in the US and in the world. It is hoped that the combined precision data from the quark and lepton sectors will one day provide a key to the nature of the underlying physics. This project provides theoretical foundations needed to support these experimental breakthroughs, in particular, by giving a more rigorous description of neutrino-nucleus interactions. It also serves as an excellent training ground for students. This research focuses on a specific piece of physics that plays a crucial role in modelling neutrino interactions at GeV energies: the nucleon axial form factor. It describes the structure of the nucleon which is not a point-like particle but has a structure that is still not well known. The PI and her collaborators develop an analytical framework to accurately model this form factor, based on the methods of chiral perturbation theory and dispersive techniques. Moreover, a bridge to numerical evaluations on the lattice is established by applications of various analytical constraints, such as current conservation. Agreement with various electron scattering data is also explored. These studies are extended to pion production in neutrino-nucleon scattering where a bridge between the low energy knowledge relying on chiral perturbation symmetry and higher energies needs to be established. This research supports the state-of-the-art nuclear physics experiments at Thomas Jefferson Laboratory, particularly GlueX or CLAS, as well as the upcoming precision neutrino-nucleus scattering experiments at Fermilab and worldwide. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.