New Precision Limit on the Strange Vector Form Factors of the Proton

TL;DR

This paper reports a precise measurement of the strange quark contributions to the proton's electromagnetic form factors, finding results consistent with zero and significantly constraining their possible size.

Contribution

It provides the most precise limit to date on the strange vector form factors of the proton, refining our understanding of strange quark effects in nucleon structure.

Findings

Strange quark contributions are consistent with zero within experimental uncertainties.

The measurement constrains strange form factors to be less than a few percent of the proton form factors.

Results align with previous data, reinforcing the negligible role of strange quarks in proton structure.

Abstract

The parity-violating cross-section asymmetry in the elastic scattering of polarized electrons from unpolarized protons has been measured at a four-momentum transfer squared Q2 = 0.624 GeV and beam energy E =3.48 GeV to be A_PV = -23.80 +/- 0.78 (stat) +/- 0.36 (syst) parts per million. This result is consistent with zero contribution of strange quarks to the combination of electric and magnetic form factors G_E^s + 0.517 G_M^s = 0.003 +/- 0.010 (stat) +/- 0.004 (syst) +/- 0.009 (ff), where the third error is due to the limits of precision on the electromagnetic form factors and radiative corrections. With this measurement, the world data on strange contributions to nucleon form factors are seen to be consistent with zero and not more than a few percent of the proton form factors.