PUMA, or antiProton Unstable Matter Annihilation, is a compact experiment designed to carry antiprotons from CERN’s Antimatter Factory to the Laboratory’s ISOLDE facility, for research into exotic nuclear-physics phenomena. Antiprotons are the antimatter counterparts of the familiar protons that together with neutrons make up the nuclei of atoms.
The experiment consists of a two-zone trap for antiprotons and a particle detector. Antiprotons are stored in the first trap. The second mixes antiprotons and unstable atomic nuclei that are produced at ISOLDE but decay too fast to be carried anywhere themselves. The particle detector records the products of antiproton-nucleus annihilations occurring in the second trap.
The goal is to find out the relative densities of protons and neutrons at the surface of such nuclei. These densities could reveal exotic nuclear features such as thick neutron “skins” or extended “halos” of protons or neutrons. Such knowledge could shed light on the nuclear processes within neutron stars.
PUMA was approved in March 2021 and is expected to begin operation in 2023.