Nuclear Physics Seminars

Elastic electron-nucleon scattering has provided a wealth of information about the electromagnetic structure of nucleons through measurement of the Sachs electromagnetic form factors over a wide range of \(Q^2\) . These data can be used to extract properties such as the spatial distribution and flavor decomposition of their charge and magnetization. At larger \(Q^2\) , deviation from expected dipole-like behavior for the proton has provided new insight and questions into proton structure and the choice of measurement technique. The nucleon, however, also has a weak structure of which relatively little is known. When scattering occurs by the exchange of a weak vector boson, one gains access to the axial vector form factor, \(F_A(Q^2)\). \(F_A(Q^2)\) is the least well-known of the nucleon form factors with most data coming from neutrino-nucleus scattering for which few experiments exist. These measurements suffer from poor statistics, poorly constrained kinematics and, except for a recent ν −p experiment by the MINERνA collaboration, all require nuclear corrections. Further, these experiments have assumed a dipole form factor with no justification. In this talk I will describe an experiment that would be the first to measure \(F_A\) using \(p(e^-,n)v_e\). The reaction will be identified from much larger background processes using a time of-flight detector with < 100 ps resolution followed a neutron calorimeter, and will capitalize on the parity-violating asymmetry of the reaction with respect to the incident electron helicity. The experiment is designed to run at Jefferson Lab using, in part, the SBS spectrometer system for veto of charged recoil particles. Data from this experiment will shed light on the weak structure of the nucleon at precise kinematics and will reduce one of the largest systematic uncertainties in neutrino oscillation experiments. This work is supported by the U.S. Department of Energy and the Thomas Jefferson National Accelerator Facility.