Cooled Antiproton Beam Research Articles

The CERN low-energy antiproton programme: the synchrotrons

When ideas for the SPS proton–antiproton collider firmed up, it was realized that the abundant production of antiprotons offered a further unique possibility: the deceleration and cooling would provide low-energy antiproton beams of unprecedented intensity and purity. A proposal was made to add a small facility for experiments with cooled antiproton beams in the energy range of 5 to 1200MeV. This was to become the Low-Energy Antiproton Ring, LEAR. Originally thought to only exist parasitically on the antiproton production for the SPS Collider, the project took on an ever-growing importance and, owing to its great successes, has even outlived the SPS Collider. It continues to this day in the simplified form of the Antiproton Decelerator, AD. Our paper describes the accelerator aspects of this venture.

The exclusive reaction [formula omitted

The Fermilab E835 Collaboration has studied Charmonium production using a gas jet hydrogen target, the virtually monoenergetic stochastically cooled antiproton beam and a large acceptance shower spectrometer. Until now our studies have featured electromagnetic final states, mostly the e + e − decay of J ψ or ψ′, and γγ decay of η c , X c0 , or X c2 . For the first time in hadronic Charmonium production, hadronic annihilation channels have been clearly identified: π 0 π 0 and ηη at the X c0 resonance. This has required a parameterization of the non-resonant partially interfering final state channels. Our studies contribute to a clearer and improved understanding of the p p annihilation process.

Charmonium states at the Fermilab antiproton accumulator. New results from E835

Experiment E835 has collected a large sample of charmonium states using a hydrogen jet and the virtually monoenergetic stochastically cooled antiproton beam. We present an improved measurement of the ξ c0 mass and width, preliminary results of analysis of the ξ c0 decay to μ 0 μ0 and γγ and the final value of our measurements of the η c parameters.

Beam decelerations with variable momentum compaction in the Fermilab Antiproton Accumulator

For the study of charmonium resonances above and including the χ c0 , Fermilab experiment E-835 required an intense and stochastically cooled antiproton beam with kinetic energies from 8 GeV (the injection energy of the Accumulator) down to 4 GeV . We developed a scheme in which the momentum compaction factor of the machine was changed as the antiprotons were decelerated, so that the energies of interest to the experiment were kept above transition. The scheme was used during the E-835 10-month run of the year 2000. Here we describe the design criteria, operational procedures and diagnostic tools we used to exploit the machine as an efficient antiproton decelerator. The machine performance during data taking is also discussed, in relation to the main experimental requirements.

The exclusive reaction [formula omitted

The Fermilab E835 Collaboration has studied Charmonium production using a gas jet hydrogen target, the virtually monoenergetic stochastically cooled antiproton beam and a large acceptance shower spectrometer. Until now our studies have featured electromagnetic final states, mostly the e + e − decay of J ψ or ψ′, and γγ decay of η c , χ c0 , or χ c2 . For the first time in hadronic Charmonium production, hadronic annihilation channels have been clearly identified: π 0 π 0 and ηη at the χ c0 resonance. This has required a parameterization of the non-resonant partially interfering final state channels. Our studies contribute to a clearer and improved understanding of the p p annihilation process.

The physics of SuperLEAR

The physics topics accessible with new high-energy cooled antiproton beams are discussed following the guidelines of the proposed SuperLEAR facility at CERN. This review attempts to paint the overview of the envisioned physics program as it is presently discussed. Conventional and exotic meson searches extending to the charm quark sector highlight the plans and are accompanied by a broad program in hyperon-antihyperon production, two-body reaction studies, and interesting tests using nuclear targets. The emphasis is on realistic opportunities with the further aim to point out the most meaningful first-generation experiments.

Prospects for electron cooling of antiprotons at low energies

The motivation of using electron cooling in low-energy antiproton storage rings and the expected cooling performance are discussed. Results obtained recently, during the first operation of electron cooling in LEAR at CERN with a 50 MeV proton beam, are summarized, concerning in particular the equilibrium beam properties, the recombination between cooling electrons and cooled protons, and the deceleartion of acceleration of protons by friction in the electron beam. Conclusions are drawn for the formation of antihydrogen with the cooled antiproton beam, and for the deceleration of antiprotons to energies close to or below 1 MeV.