Observation of Cold Antihydrogen

The simplest electrical neutral system made entirely of antimatter is the antihydrogen atom (H-bar 0) consisting of a positron (e+) orbiting an antiproton (p-bar ). The first H-bar 0 atoms produced in p-bar -A collisions at the Low Energy Antiproton Ring (LEAR) at CERN have been observed in 1995 [G. Baur, et al., Phys. Lett. B 368 (1996) 251] and were confirmed thereafter at Fermilab [G. Blanford, et al., Phys. Rev. Lett. 80 (1998) 3037]. However, low production rates and high velocity of these exotic atoms made it impossible to even think of using them for high precision spectroscopy or studies of the gravitational interaction.At the Antiproton Decelerator (AD) of CERN trap experiments are in operation, where cold H-bar 0 atoms are synthesized 'at rest' starting from clouds of p-bar 's and e+'s trapped at temperatures of a few Kelvin. Only if the produced H-bar 0 atoms once are trapped in a magnetic field arrangement meaningful studies can be done. The challenging prospect is the comparison of atomic transitions in antihydrogen and hydrogen atoms where the latter have been measured with highest precision [R. Holzwarth, et al., Phys. Rev. Lett. 85 (2000) 2264, M. Niering, et al., Phys. Rev. Lett. 84 (2000) 5496]Within local relativistic quantum field theories CPT is an exact symmetry which predicts absolutely identical spectral lines and thus any deviation in the spectroscopy of antimatter from matter atoms would require an extension of the standard model by CPT violation components.Thus, such precision experiments just have to be done and here a report is presented on first steps towards the production of cold H-bar 0 atoms and subsequent studies of their physics properties