Antiproton decelerator

The recent advances in producing, trapping and cooling antiprotons and positrons opened the possibility of antihydrogen formation in laboratory. This may allow the studies of antimatter and tests of fundamental physical principles such as charge - parity - time ( CPT ) invariance or the weak equivalence principle (WEP) for antiparticles. Such experiments are planned at the newly built CERN AD (Antiproton Decelerator) within ASACUSA, ATRAP and ATHENA projects, which have just started their operations. 

A method to observe microwave resonances in antiprotonic helium has been proposed and is being prepared for the coming antiproton decelerator (AD) ring at CERN [36]. It is called 2-laser-microwave triple resonance method, which has the following steps. 

A new antiproton facility AD (antiproton decelerator) has been completed at CERN and a series of experimental programs are in progress. These include more systematic studies of the structure and formation of pHe+, higher precision laser spectroscopy, microwave spectroscopy [36] and search for type-II antiprotonic helium based on the excited helium [37]. 

The production and spectroscopy of antihydrogen (p-e+ = H) is one of the central topics at the Antiproton Decelerator (AD) of CERN. The two other approved experiments, ATHENA [5] and ATRAP [6] are dedicated to antihydrogen... 

The upcoming Antiproton Decelerator (AD) [1] at CERN allows the formation and precision spectroscopy of antiprotonic atoms. Among the three approved experiments, the ASACUSA collaboration [2] will as part of its program continue experiments with antiprotonic helium that were previously performed by the PS205 collaboration [3] at the now closed Low Energy Antiproton Ring (LEAR) of CERN. Antiprotonic helium consisting of an alpha particle, an antiproton, and an electron (He++ —p — = pHe+), was found to have lifetimes in the... 

The Barkas effect, which makes the stopping power for negative and positive particles different in matter, can also be included there as a term zLiiP ) it makes the energy loss for a slow negative particle lower than for a positive one under identical conditions due to polarization of the medium. This effect is studied in detail at the Antiproton Decelerator at CERN (Moeller et al. 2002). 

CPT invariance is so far fiilly supported by the available experimental evidence and it is absolutely fundamental in field theory. Nevertheless, there are many experiments trying to test it. The simplest way to do that is to compare the mass or charge of particles and antiparticles. The most precise measurement of this type is that of the relative mass difference between the neutral K meson and its antiparticle that has so far been found to be less than 10 (Amsler et al. 2008). In 1999, an Antiproton Decelerator facility (CERN 2009) was constructed at the European Particle Physics Laboratory, CERN, in order to test the CPT invariance by comparing the spectra of hydrogen and antihydrogen, the latter being the bound state of an antiproton and a positron (see Chap. 28 in Vol. 3). 

Antiproton is the only stable heavy negative particle, and so it has a special treatment. At GERN s Antiproton Decelerator (AD) antiprotons are produced with a momentum of 3.5 GeV/c when the 26 GeV proton beam of the Proton Synchrotron hits an iridium target. 

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