Measurement of the axial vector form factor from antineutrino-proton scattering

Area of Science:

• Particle Physics
• Nuclear Structure
• High-Energy Physics

Background:

• Scattering experiments with high-energy particles probe nucleon structure.
• Charged leptons measure electric charge distribution via vector form factors.
• Neutrino scattering offers a complementary probe, measuring both vector and axial vector form factors.

Purpose of the Study:

• To report the first high-statistics measurement of antineutrino-hydrogen scattering.
• To extract the nucleon transition axial form factor (F_A) from free proton targets.
• To measure the nucleon axial charge radius (r_A) without nuclear corrections.

Main Methods:

• Utilized the MINERvA experiment with a plastic scintillator target.
• Measured the antineutrino-hydrogen scattering cross-section.
• Extracted F_A(Q²) and subsequently r_A.

Main Results:

• Reported the first measurement of antineutrino-hydrogen scattering cross-section.
• Extracted the nucleon axial form factor from free proton targets.
• Determined the nucleon axial charge radius to be 0.73 ± 0.17 fm.

Conclusions:

• Antineutrino-hydrogen scattering provides a direct probe of the axial form factor, bypassing nuclear theory uncertainties.
• The results enable direct comparisons with lattice quantum chromodynamics computations.
• Advancements in understanding nucleon structure in the weak sector and improved constraints for neutrino oscillation experiments.