Precision measurement of the $e^{+}e^{-}~\rightarrow~\Lambda_{c}^{+} \bar{\Lambda}_{c}^{-}$ cross section near threshold

TL;DR

This paper reports a highly precise measurement of the e+e- to Lambda_c+ Lambda_c- cross section near threshold, revealing non-zero values and first measurements of the form factor ratio, advancing understanding of charmed baryon production.

Contribution

The study provides the first measurement of the ratio of Lambda_c electric to magnetic form factors near threshold, using high-statistics data from BESIII.

Findings

Non-zero cross section near threshold.

First measurement of |G_E/G_M| for Lambda_c.

Precise form factor ratios with uncertainties.

Abstract

The Born cross section of the $e^{+}e^{-}~\rightarrow~\Lambda_{c}^{+} \bar{\Lambda}_{c}^{-}$ process is measured with unprecedented precision using data collected with the BESIII detector at $\sqrt{s}=4574.5$, $45580.0$, $4590.0$ and $4599.5$ $\mathrm{MeV}$. The non-zero cross section near the $\Lambda_{c}^{+} \bar{\Lambda}_{c}^{-}$ production threshold is discerned. At center-of-mass energies $\sqrt{s}=4574.5$ and $4599.5 $ $\mathrm{MeV}$, the higher statistics data enable us to measure the $\Lambda_{c}$ polar angle distributions. From these, the ratio between the $\Lambda_{c}$ electric and magnetic form factors ($|G_{E}/G_{M}|$) is measured for the first time. They are found to be $1.14\pm0.14\pm0.07$ and $1.23\pm0.05\pm0.03$ respectively, where the first uncertainties are statistical and the second are systematic.