Novel method to extract the femtometer structure of strange baryons using the vacuum polarization effect

Abstract

One of the fundamental goals of particle physics is to gain microscopic understanding of the strong interaction. Electromagnetic form factors quantify the structure of hadrons in terms of charge and magnetization distributions. While the nucleon structure has been investigated extensively, data on hyperons is still scarce. It has recently been demonstrated that electron-positron annihilations into hyperon-antihyperon pairs provide a powerful tools to investigate their inner structure. We present a novel method useful for hyperon-antihyperon pairs of different types which exploits the cross section enhancement due to the vacuum polarization effect at the $J/\psi$ resonance. Using the 10 billion $J/\psi$ events collected with the BESIII detector, this allows a thorough determination of the hyperon structure . The result is essentially a precise snapshot of a $\bar{\Lambda }{\Sigma }^0$~($\Lambda {\bar{\Sigma }}^0$) pair in the making, encoded in the form factor ratio and the phase. Their values are measured to be $R=0.860\pm 0.029(stat.)\pm 0.010(syst.)$, $\Delta {\Phi }_1=(1.011\pm 0.094(stat.)\pm 0.010(syst.))\mathrm{rad}$ for $\bar{\Lambda }{\Sigma }^0$ and $\Delta {\Phi }_2=(2.128\pm 0.094(stat.)\pm 0.010(syst.))\mathrm{rad}$ for $\Lambda {\bar{\Sigma }}^0$, respectively. Furthermore, charge-parity (CP) breaking is investigated for the first time in this reaction and found to be consistent with CP symmetry.

References in corpus (9)

• Number of $J/\psi$ events at BESIII
• Precise Measurements of Decay Parameters and $CP$ Asymmetry with Entangled $\Lambda -\bar{\Lambda }$ Pairs
• Measurement of proton electromagnetic form factors in the time-like region using initial state radiation at BESIII
• High-precision determination of the electric and magnetic radius of the proton
• Hyperon electromagnetic form factors in the timelike region
• Study of CP violation in hyperon decays at Super Charm-Tau Factories with a polarized electron beam
• Production and decay of polarized hyperon-antihyperon pairs
• The electromagnetic Sigma-to-Lambda transition form factors with coupled-channel effects in the space-like region
• Polarisation observables in lepton antilepton to proton antiproton reactions including lepton mass

Cited by in corpus (2)

• Tests of CP symmetry in entangled hyperon anti-hyperon pairs at BESIII
• Observation of $\Xi (1530{)}^0$ Polarization and Determination of Its Electric and Magnetic Moments in $\psi (3686)\to \Xi (1530{)}^0\bar{\Xi }(1530{)}^0$