Measurement of the neutron timelike electric and magnetic form factors ratio at the VEPP-2000 $e^+e^-$ collider

TL;DR

This study measures the neutron's electric to magnetic form factor ratio in the timelike region at the VEPP-2000 collider, providing new insights into neutron structure in the 1890-2000 MeV energy range.

Contribution

It presents the first measurement of the neutron form factor ratio in the timelike region at these energies using the SND detector.

Findings

The ratio |GE|/|GM| ranges from 1.0 to 1.5, averaging 1.21±0.13.

The experiment was conducted at eight energy points with 83 pb⁻¹ luminosity.

The ratio was extracted from the polar angle distribution of the produced antineutron.

Abstract

In the experiment to study the e+e->n+anti n process at the VEPP-2000 $e^+e^-$ collider, the ratio |GE|/|GM| of the neutron timelike electric and magnetic form factors has been measured. The experiment was carried out with the SND detector in the center-of-mass energy range 1890-2000 MeV in eight energy points with an integrated luminosity of 83 inv.pb. The |GE|/|GM| ratio is determined by the analyzing the distribution of the polar angle of the produced antineutron. The measured |GE|/|GM| value in the energy range under study is between 1.0 and 1.5 with an average value of 1.21+-0.13.