Annihilation Phenomena and Anti-matter Atoms

Most recent answer: 01/02/2013

Can different particles and antimatter particles eliminate each other? IE a positron eliminate a proton or do they only eliminate their counterpart? Also, if we make antimatter particles in a lab, can an antimatter atom be sustained?
- Christopher Felix (age 35)
Tustin, Ca. USA
The answer to your first question is no.  For annihilation to occur all quantum numbers of the two particles must be equal in magnitude with opposite signs.  Both a positron and a proton have electronic charge +1, so that doesn't work. Secondly the positron has a property called lepton number, which is + one.  The proton has a property called baryon number, which is + one.  Its lepton number is 0.
Many experiments have shown that both lepton number and baryon number are separately conserved.  Thus a positron could not annihilate with a negatively charged antiproton even though charge conservation would be satisfied. 
The answer to your second question is yes.   You can form anti-hydrogen by mixing positrons with some anti-protons.   This has been demonstrated at the CERN accelerator laboratory in Switzerland.   You can get positrons from a strong beta decay source.  The anti-protons come from the high energy accelerator at CERN.  Many properties of anti-hydrogen should be identical to those of regular hydrogen atoms such as the magnetic moment, total mass, etc.   These predictions have been verified.


(published on 01/02/2013)