Scientists map inner structure of exotic particles with unprecedented precision
Physicists have developed a new technique to measure the internal structure of strange baryons—exotic particles found in high-energy collisions—with femtometer-scale precision. The advance, based on data from 10 billion particle collisions, could accelerate understanding of the strong nuclear force and improve models used in particle physics research and industrial applications.
Originaltitel: Extracting the femtometer structure of strange baryons using the vacuum polarization effect
<p>One of the fundamental goals of particle physics is to gain a 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 are still scarce. It has recently been demonstrated that electron-positron annihilations into hyperon-antihyperon pairs provide a powerful tool to investigate their inner structure. We present a method useful for hyperon-antihyperon pairs of different types which exploits the cross section enhancement due to the effect of vacuum polarization at the J/psi resonance. Using the 10 billion J/psi events collected with the BESIII detector, this allows a precise determination of the hyperon structure function. The result is essentially a precise snapshot of the (Lambda) over bar Sigma(0)(Lambda(Sigma) over bar (0)) transition process, encoded in the transition form factor ratio and phase. Their values are measured to be R = 0.860 +/- 0.029(stat.) +/- 0.015(syst.), Delta phi((Lambda) over bar Sigma 0) = (1.011 +/- 0.094(stat.) +/- 0.010(syst.)) rad and Delta phi(Lambda(Sigma) over bar0) = (2.128 +/- 0.094(stat.) +/- 0.010(syst.)) rad. Furthermore, charge-parity (CP) breaking is investigated in this reaction and found to be consistent with CP symmetry.</p>