The 'charm
quark' is a second-generation quark with a charge of +(2/3)''
e''. It is the third most massive of the quarks, at 1.3
GeV (a bit more than the mass of the
proton). It was predicted in 1970 by
Sheldon Glashow,
John Iliopoulos, and
Luciano Maiani, and first observed in November 1974, with the simultaneous discovery of the
J/ψ charm particle at
SLAC (Stanford Linear Accererator Center) by a group led by
Burton Richter and at
BNL (Brookhaven National Laboratory) by a group led by
Samuel C. C. Ting. The particle was named J by the BNL group and
ψ by the SLAC group; when the naming controversy could not be resolved, the compromise
J/ψ was adopted.
:
Hadrons containing charm quarks
Some of the
hadrons containing charm quarks include:
★ D
mesons contain a charm quark (or its
antiparticle) and an
up or
down quark.
★ D
s mesons contain a charm quark and a
strange quark.
★ There are many
charmonium states, for example the
J/ψ particle. These consist of a charm quark and its antiparticle.
★ Charmed
baryons have been observed, and are named in analogy with strange baryons (e.g. Λ
c+).