Axial-Vector Form Factor (AVFF) from an electron-to-neutrino process with a proton

Interest in the reaction e+p→ν+n has been very high since the 1980s, as it provides the access to the weak charged current process. Recently, the Minerνa collaboration published new results for the Axial Vector Form Factor (AVFF) using the inverse reaction, which however has limited accuracy due to the uncertainty in the neutrino energy. We have found a practical configuration of the experiment with an electron beam for the momentum transfer of 1 (GeV/c)². This is possible thanks to the high intensity and polarization of the electron beam at JLab.

Among the six elastic nucleon form factors, AVFF is the least known. The measurement of the AVFF is important for understanding several processes from the proton, e.g. the Wide Angle Compton Scattering and for constraining the nucleon GPDs.

Despite the very low cross-sections, the result could be achieved by an experiment with a high level of background particle suppression in the final state. The combination of a high current polarized electron beam with helicity flips, which enables/disables the weak process, the SBS spectrometer at JLab as an electron/pion veto arm, and a neutron detection arm, for tagging and counting the recoiling neutrons with 100 picosecond time and good angle resolution, will be used.

The status of the proposal development for the measurement of the AVFF at Q²=1 (GeV/c)² (and potentially at other transferred momenta) at JLab will be reviewed, with highlights on the technique and the key parameters.