BESIII results on time-like baryon form factors

Helmholtz-Institut Mainz, Germany

^* e-mail: adbeyssi@uni-mainz.de

Published online: 18 October 2019

Abstract

This contribution reports on the recent measurements of baryon electromagnetic form factors at the BESIII experiment in Beijing. The Beijing e⁺e ⁻ collider BEPCII is a double-ring symmetric collider running at $\sqrt{s}$ between 2.0 and 4.6 GeV. Baryon electromagnetic form factors can be measured at BESIII in direct e⁺e⁻-annihilation and in initial state radiation processes. Based on the data collected by the BESIII detector at 12 center of mass energies between 2.23 and 3.67 GeV, the measured ${{\displaystyle e}}^{+}{{\displaystyle e}}^{-}\to \stackrel{-}{p}p$ cross section and the time-like proton form factor are presented. Preliminary results from the analysis of the initial state radiation process ${{\displaystyle e}}^{+}{{\displaystyle e}}^{-}\to \stackrel{-}{p}p\gamma$ using a data set of 7.408 fb⁻¹ collected at center of mass energies between 3.773 and 4.6 GeV, are also shown. The cross sections for $\begin{array}{l}{{\displaystyle e}}^{+}{{\displaystyle e}}^{-}\to \stackrel{-}{{{\displaystyle \Lambda }}_c^{-}}{{\displaystyle \Lambda }}_c^{+}\\ math5-----{{\displaystyle e}}^{+}{{\displaystyle e}}^{-}\to \stackrel{-}{\Lambda }\Lambda \end{array}$ and ${{\displaystyle e}}^{+}{{\displaystyle e}}^{-}\to \stackrel{-}{\Lambda }\Lambda$ are measured near threshold with unprecedented precision. Preliminary results on the first measurement of the ^_c form factor ratio |GE|/|GM| are also given. Ongoing analysis based on the high luminosity energy scan from 2015 and from radiative return at different $\sqrt{s}$ are also described.