Upsilon particle

Upsilon ()
A plot of the invariant mass of muon pairs, from the Upsilon particle discovery paper. The peak at about 9.5 GeV represents the particle itself.
Composition:	Composite: Quarks: 1 bottom, 1 antibottom
Family:	Hadron
Group:	Meson
Electric charge:	0 C
Spin:	1

The Upsilon particle () 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 1.21x10^-20 seconds and a mass about 10 GeV.

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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 J/ψ particle is the analogous state made from charm quarks.
• List of mesons

References

1. Hom, D.C., et al. (1977). "Observation of a Dimuon Resonance at 9.5 Gev in 400-GeV Proton-Nucleus Collisions". Phys. Rev. Lett. 39: 252-255.
2. Yoh, John (1998). "The Discovery of the b Quark at Fermilab in 1977: The Experiment Coordinator's Story". AIP Conf. Proc. 424: 29-42.
3. Technical data (pdf file) from Particle Data Group (From 2005 update of S. Eidelman et al. (2004). "Review of Particle Physics". Phys. Lett. B 592: 1.)