Scientists measure exotic particle collisions that could solve neutron star mystery
Researchers have made the first direct measurements of how rare particles called sigma baryons interact with atomic nuclei, filling a critical gap in understanding the composition of neutron stars. The findings could help resolve a decades-old physics puzzle about what prevents neutron stars from collapsing under their own weight—knowledge that ultimately informs models of extreme cosmic objects.
Originaltitel: First measurement of Σ<sup>+</sup>𝑛 → Λ𝑝 and Σ<sup>+</sup>𝑛 → Σ<sup>0</sup>𝑝 cross sections via Σ<sup>+</sup>-nucleus scattering at an electron-positron collider
<p>Using (1.0087±0.0044)×1010 𝐽/𝜓 events collected with the BESIII detector at the BEPCII storage ring, the reactions Σ+𝑛 → Λ𝑝 and Σ+𝑛 → Σ0𝑝 are studied, where the Σ+ baryon is produced in the process 𝐽/𝜓→Σ+‾‾‾Σ− and the neutron is a component of the 9Be, 12C, and 197Au nuclei in the beam pipe. Clear signals of these two reactions are observed for the first time. Their cross sections are measured to be 𝜎(Σ++9Be → Λ+𝑝+𝑋)=(45.2±12.1stat±7.2sys) mb and 𝜎(Σ++9Be→Σ0+𝑝+𝑋)=(29.8±9.7stat±6.9sys) mb for a Σ+ average momentum of 0.992GeV/𝑐, within a range of ±0.015GeV/𝑐, where 𝑋 represents the residual nucleus. This is the first study of Σ+-nucleon scattering at an electron-positron collider. The measured results serve as a significant element in enhancing the comprehensive understanding of hyperon-nucleon interactions, and also constitute an important factor in resolving the “hyperon puzzle” of neutron stars.</p>