Antihydrogen - Characteristics

Characteristics

According to the CPT theorem of particle physics, antihydrogen atoms should have many of the characteristics regular hydrogen atoms have; i.e., they should have the same mass, magnetic moment, and transition frequencies (see atomic spectroscopy) between their atomic quantum states. For example, excited antihydrogen atoms are expected to glow with the same color as that of regular hydrogen. Antihydrogen atoms should be attracted to other matter or antimatter gravitationally with a force of the same magnitude that ordinary hydrogen atoms experience. This would not be true if antimatter had negative gravitational mass, which is considered highly unlikely, though not yet empirically disproven (see gravitational interaction of antimatter).

When an antihydrogen atom comes into contact with ordinary matter, its constituents quickly annihilate. The positron, which is an elementary particle, annihilates with an electron, with their mass-energy being released as gamma rays. The antiproton, on the other hand, is made up of antiquarks that combine with the quarks in either neutrons or protons in normal matter; the annihilation results in high-energy pions. These pions in turn quickly decay into muons, neutrinos, positrons, and electrons. If antihydrogen atoms were to be suspended in a perfect vacuum, however, they should survive indefinitely.