&Bullet; physics 14, p85

Antineutrons and hyperons are difficult to make and study, but the researchers propose a new approach that would create these particles using existing and planned accelerators.

In order to study particles that do not normally occur in nature, physicists have to generate them in accelerators. However, some particles have proven particularly difficult to generate. Chang-Zheng Yuan from the Institute of High Energy Physics, China, and Marek Karliner from Tel Aviv University, Israel, now propose a way to create two such types of particles – antineutrons and hyperons – using existing and planned accelerators [1] . The ability to produce these elusive particles without special facilities could accelerate research in nuclear and particle physics, such as the study of hyperon-nucleon interactions and the role of hyperons in neutron stars.

Current methods only produce these particles in relatively small quantities. In addition, some production routes – such as the proton-antiproton annihilation reactions that produce antineutrons – produce particles whose momentum and direction are difficult to measure, making them unsuitable for many research purposes. In their new approach, Yuan and Karliner propose to exclude antineutrons and hyperons

$J/\psi$

Mesons. These particles are a promising source because they often decay into antineutrons or hyperons and are themselves a relatively common product of electron-positron annihilations. The researchers could also determine the momentum of particles generated in this way by measuring other particles that bounce back from them during the decay reaction.

The researchers consider the Beijing Spectrometer (BESIII) experiment, a device for studying charm quarks, tau leptons and other particles, to be a proof of concept. In four recent trials, BESIII produced a total of 10 billion

$J/\psi$

meson events. Yuan and Karliner estimate that this sample of new

$J/\psi$

Mesons would have produced about eight million antineutrons, which would be suitable for studies. future

$J/\psi$

“Factories” will produce orders of magnitude more of these particles, it is said.

–Erika K. Carlson

Erika K. Carlson is Corresponding Editor for physics based in New York City.

## References

1. CZ Yuan and M. Karliner, “Cornucopia of antineutrons and hyperons from a super
$J/\psi$

Factory for high-precision experiments in next-generation nuclear and particle physics “, Phys. Rev. Lett.127, 012003 (2021).

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