Definitions

# Charm quark

The charm quark is a second-generation quark with an electric charge of +(2/3)e. It is the third most massive of the quarks, at about (roughly one and a half times 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 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 was adopted. The quark itself derived its name from the "charmed" life the J/ψ leads, having a half-life a thousand times longer than had been predicted theoretically.

$C = N_c - N_\left\{overline\left\{c\right\}\right\}$