Speaker
Description
The nucleon Axial-Vector Form Factor (AVFF) remains the least constrained among the nucleon form factors, with its normalization well-determined only at $Q^2 = 0$ from $\beta$-decay. Existing measurements at higher $Q^2$ rely on neutrino quasi-elastic scattering on nuclei, which suffer from limited statistics, dependence on nuclear models, and systematic uncertainties in neutrino beam energy. Accurate, independent knowledge of the AVFF is vital for interpreting modern neutrino-oscillation experiments (such as DUNE), in addition to constraining Generalized Parton Distributions (GPDs), and understanding nucleon dynamics inaccessible via purely electromagnetic probes.
To address this, we propose a direct AVFF measurement via the weak charged-current inverse $\beta$-decay process, $e^- + p \rightarrow \nu_e + n$, using the high-intensity, polarized electron beam at Jefferson Lab. Optimized for $Q^2 = 1\text{ (GeV/c)}^2$, the experiment overcomes an extremely low cross-section by maximizing the signal-to-background ratio. This is achieved via rapid beam helicity flips to isolate the weak process, the Super BigBite Spectrometer (SBS) as a suppressive electron/pion veto, and a high-precision neutron arm featuring 100-picosecond time resolution for recoil tagging.