And still more!
Many new particles were discovered with the advent of particle accelerators in the 1950’s (e.g., the Cosmotron at Brookhaven, the Bevatron at Berkeley).
- Baryons: particles with lifetimes ~ 10-10 seconds, ultimately decaying to protons. Anti-particles also seen (anti-proton in 1955)
- Mesons: particles with lifetimes ~ 10-8 seconds, typically lighter than the proton and never decaying into protons.
- Resonances: Extremely short-lived (~10-25 sec). Not seen directly but existence inferred.
- Baryons: Total = 53 (?????????????????
- Mesons: Total = 25 (????????????K*????
Too many particles to all be “elementary” - must be some underlying pattern!