The CPT theorem and the Weak Equivalence Principle are foundational
principles on which the standard description of the fundamental interactions is
based. The validity of such basic principles should be tested using the largest
possible sample of physical systems. Cold neutral antimatter (low-energy
antihydrogen atoms) could be a tool for testing the CPT symmetry with high
precision and for a direct measurement of the gravitational acceleration of
antimatter. After several years of experimental efforts, the production of
low-energy antihydrogen through the recombination of antiprotons and positrons
is a well-established experimental reality. An overview of the ATHENA
experiment at CERN will be given and the main experimental results on
antihydrogen formation will be reviewed.Comment: Proceedings of the XLIII International Meeting on Nuclear Physics,
Bormio (Italy), March 13-20 (2005). 10 pages, 4 figures, 1 tabl