The BESIII collaboration recently reported a study of hyperon-nucleon reaction Ξ⁰n→Ξ^-p with “Ξ⁰beam” from the decay J/ψ→Ξ⁰anti-Ξ⁰based on 10 billion J/ψ data. This is the first study of hyperon-nucleon interaction in electron-positron collisions,opening a new direction for such research.The results werepublished recently in Physics Review Letters on June 21, 2023 [Phys. Rev. Lett. 130, 251902 (2023)].

Scattering experiments of high energy particle beams bombarding target materials have been of great significance for studying the inner structure of matter and the fundamental interactions. Charged long-lived particle beams such as π^±and K^±can be easily produced, and relevant research results have been very rich. However, limited by the availability and short-lifetime of hyperon beams, the progress of corresponding research is very slow, although measurements of these hyperon beams bombarding target materials are crucial for understanding non-perturbative quantum chromodynamics. In addition, the hyperon-nucleon reaction also can be used to search for the postulated H-dibaryon, which has strangeness -2 and valence quark structure uuddss. Furthermore, the study of hyperon-nucleon interaction is also important to determine the equation of state for dense nuclear matter and to understand the so-called “hyperon puzzle” of neutron star.

In this work, a novel method is used to study hyperon-nucleon interaction based on hyperons produced in the decay of10 billion J/ψ events collected with the BESIII detector at the BEPCII storage ring, and the beam pipe can be taken as thetarget material (figure 1). The reaction Ξ⁰n→Ξ^-p is observed with about 20 signal events for the first time (figure 2), and the cross section of the reaction Ξ⁰+⁹Be→Ξ^-+p+⁸Be is determined to be (22.1±5.3_stat±4.5_syst) mb at the Ξ⁰momentum of 0.818 GeV/c. If the effective number of reaction neutrons in a⁹Be nucleus is taken as 3, the cross section of Ξ⁰n→Ξ^-p for a single neutron is determined to be (7.4±1.8_stat±1.5_syst) mb, consistent with theoretical hypothesis.In addition, no any significant H-dibaryon signals are observed in the Ξ^-p final state for this reaction process. Other hyperons and nucleon interactions can also be studied in this way, such as Λ and Σ.

In this research work, Dr. Jielei Zhang from the School of Physics and Electronics made important contributions. This work is supported by the National Natural Science Foundation of China and Henan University.

FIG. 1. Schematic diagram of the beam pipe, the length units are centimeter (cm).

FIG. 2. Distribution of M(Λπ^-) in data.

Further reading:

PRL publication link:https://link.aps.org/doi/10.1103/PhysRevLett.130.251902

arXiv link:https://arxiv.org/abs/2304.13921