Speaker
Description
Antinucleon ($\bar{p}$ and $\bar{n}$) interactions with matter were extensively investigated at the CERN Low Energy Antiproton Ring (LEAR) for more than a decade throughout the 1980s and 1990s. Several series of systematic measurements of their cross sections on protons and nuclei led to significant advances in our understanding of hadronic interactions involving antimatter.
However, experimental data on low-energy $\bar{n}$ scattering remain scarce even today, thus limiting our knowledge of S-wave antinucleon-nucleon and antinucleon-nucleus interactions.
Recently, a collaboration of Japanese and European researchers has proposed a novel production scheme to provide very low-energy $\bar{n}$s and address this gap [1]. The leading idea is to exploit the backward-emitted $\bar{n}$s in the charge-exchange reaction ($\bar{p}$p → n$\bar{n}$ ), which can feature momenta down to a minimum value of 9 MeV/c, corresponding to a kinetic energy of only 43 keV. Such energies are well suited for the study of pure S-wave antinucleon-nucleon and antinucleon-nucleus interactions.
Preliminary tests indicate that such a low-energy $\bar{n}$ production scheme can be implemented at the CERN Antiproton Decelerator (AD) by using a modified extraction scheme, allowing the delivery of $\bar{p}$s at an intermediate momentum of 300 MeV/c.
[1] C. Amsler et. al, Letter of Intent, CERN-SPSC-2025-010 (2025) 1.