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
Statistical behavior:	Hadron
Group:	Meson
Symbol(s):	ϒ
Antiparticle:	Self
Discovered:	E288 collaboration
Mass:	9.46030(26) GeV/c2
Electric charge:	0 C
Spin:	1

The Upsilon meson (ϒ) is a flavorless meson formed from a bottom quark and its antiparticle. It was discovered by the E288 collaboration, 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.

[edit] See also

• Oops-Leon, an erroneously-claimed discovery of a similar particle at a lower mass in 1976.
• Quarkonium, the general name for mesons formed from a quark and the corresponding antiquark.
• The φ particle is the analogous state made from strange quarks.
• The J/ψ particle is the analogous state made from charm quarks.
• List of mesons

[edit] References

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

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