Upsilon meson

Upsilon (ϒ)

A plot of the invariant mass of muon pairs, from the Upsilon particle discovery paper. The peak at about 9.5 GeV is due to the contribution of the Upsilon meson.
Composition	bb
Statistics	Bosonic
Interactions	Strong, weak, Electromagnetic, Gravity
Symbol	ϒ
antiparticle	Self
Discovered	E288 experiment (1977)
Types	1
Mass	9.46030(26) GeV/c2
mean lifetime	1.21×10−20 s
electric charge	0 e
Spin	1
Isospin	0
Hypercharge	0
Parity	-1
C parity	-1

The Upsilon meson (ϒ) is a quarkonium state (i.e. flavourless meson) formed from a bottom quark and its antiparticle. It was discovered by the E288 experiment team, headed by Leon Lederman, at Fermilab in 1977, and was the first particle containing a bottom quark to be discovered because it is the lightest that can be produced without additional massive particles. It has a lifetime of 1.21×10⁻²⁰ s and a mass about 9.46 GeV/c² in the ground state.

See also

• Oops-Leon, an erroneously-claimed discovery of a similar particle at a lower mass in 1976.
• The Phi meson particle is the analogous state made from strange quarks.
• The J/Psi particle is the analogous state made from charm quarks.
• List of mesons

References

• D.C. Hom (1977). "Observation of a Dimuon Resonance at 9.5 Gev in 400-GeV Proton-Nucleus Collisions". Physical Review Letters 39 (5): 252–255. doi:10.1103/PhysRevLett.39.252. Bibcode: 1977PhRvL..39..252H. http://lss.fnal.gov/archive/1977/pub/Pub-77-058-E.pdf. 
• J. Yoh (1998). "The Discovery of the b Quark at Fermilab in 1977: The Experiment Coordinator's Story". AIP Conference Proceedings 424: 29–42. doi:10.1063/1.55114. Bibcode: 1998AIPC..424...29Y. http://lss.fnal.gov/archive/1997/conf/Conf-97-432-E.pdf. 
• S. Eidelman et al. (Particle Data Group) (2004). "Review of Particle Physics – ϒ meson". Physics Letters B 592 (1–4): 1. doi:10.1016/j.physletb.2004.06.001. Bibcode: 2004PhLB..592....1P. http://pdg.lbl.gov/2005/listings/m049.pdf. 

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