Method for measuring the proton charge radius from the time-like region

Author:

Yong-Hui Lin, Feng-Kun Guo, Ulf-G. Meißner

Keyword:

High Energy Physics - Phenomenology, High Energy Physics - Phenomenology (hep-ph), High Energy Physics - Experiment (hep-ex), Nuclear Experiment (nucl-ex), Nuclear Theory (nucl-th)

journal:

date:

2023-09-13 16:00:00

Abstract

We propose a novel method for measuring the proton charge radius. The method explores the facts that the Dalitz decay $J/\psi \to p\bar{p}e^+e^-$ contains the proton form factors and the measurable lowest four-momentum transfer squared value can be as low as $\sim 4m_e^2= 1.05\times10^{-6}$ GeV$^2$ in the time-like region. We identify a kinematic region where the proton form factors are essential and propose a method for subtracting the background from the data. It is estimated that the proton charge radius can be measured to a precision of 0.04 fm at the BESIII setup and one order of magnitude better at the future Super $\tau$-Charm Facility. Furthermore, the same method can be used to measure the charge radii of charged hyperons, which are otherwise difficult to access.

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