AMBER, or Apparatus for Meson and Baryon Experimental Research, is the successor to the COMPASS experiment, which concluded in 2022.
AMBER directs secondary particle beams from the Super Proton Synchrotron onto various targets to study hadrons such as protons, antiprotons, pions and kaons.
In its first phase of operation, AMBER aims to achieve three objectives. The first is to determine the rates at which antiprotons are produced in proton–hydrogen and proton–helium collisions. Knowledge of such rates will help to increase the sensitivity of indirect searches for dark matter. The second is to measure with high precision the spatial spread of the proton’s electric charge using high-energy muons for the first time, with a view to helping to resolve the proton-radius puzzle. The third is to measure the momenta of the quarks and gluons that form pions and kaons, in order to shed light on how hadrons get their mass.
The second phase of AMBER will focus on unique measurements taken with an intense beam of kaons. These will involve mapping the spectrum of excited states of hadrons containing a strange quark; measurements of prompt, kaon-induced production of photons in order to study the quark and gluon structure of kaons; measurements of near-miss collisions between kaons and atomic nuclei to determine how kaons respond to external electric and magnetic fields; and measurements of the electric charge distribution inside unstable hadrons.
AMBER was approved by the CERN Research Board in 2020, started taking data in 2023 and released its first results in 2024.