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	b b
Statistics	Bosonic
Family	Hadrons
Symbol	ϒ
Antiparticle	Self
Discovered	E288 collaboration
Mass	9.46030(26) GeV/c2
Electric charge	0 e
Spin	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 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 in the ground state.

See also

• Oops-Leon, an erroneously-claimed discovery of a similar particle at a lower mass in 1976.
• 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