New Features in the Electromagnetic Structure of the Neutron

Abstract

Here we present new results for the Born cross section and the effective form factor of the neutron at the center-of-mass energies $\sqrt{\mathbf{s}}$ between 2.0 and 3.08 GeV, using 18 data sets corresponding to an integrated luminosity of 647.9 pb${}^{-1}$ from e${}^{+}$e${}^{-}$ annihilation reactions collected at the BESIII experiment. The process $e^{+}{e}^{-}\to n\bar{n}$ is analyzed with three individual categories to improve the efficiency of $n\bar{n}$ reconstruction. The cross section of $e^{+}{e}^{-}\to n\bar{n}$ is measured at 18 c.m. energies where the best precision is 8.1\% at $\sqrt{s}=2.396$ GeV. The corresponding effective form factors are extracted under the assumption $|G_E|=|G_M|$. Our results improve the statistical precision on the neutron form factor by more than a factor of 60 over previous measurements from the FENICE and DM2 experiments and usher in a new era where neutron form factor data from annihilation in the time-like regime is on par with that from electron scattering experiments. In addition, an oscillatory behavior of the effective form factor observed for the proton is discussed for the neutron.

21 pages, 11 figures, 6 tables

References in corpus (7)

• High-precision determination of the electric and magnetic form factors of the proton
• Interplay of Spin and Orbital Angular Momentum in the Proton
• Study of the process $e^{+}{e}^{-}\to n\bar{n}$ at the VEPP-2000 $e^{+}{e}^{-}$ collider with the SND detector
• Periodic interference structures in the time-like proton form factor
• Study of the process $e^{+}{e}^{-}\to p\bar{p}$ via initial state radiation at BESIII
• Trigger efficiencies at BES III
• Equation of state constraints from multi-messenger observations of neutron star mergers

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