Quarks: Six Flavours & Charges

• A quark is a fundamental particle. There are six kinds, called flavours. Each one carries a charge that is a fraction of the electron charge $e$.
• up, charm and top each have charge $+\tfrac{2}{3}e$.
• down, strange and bottom each have charge $-\tfrac{1}{3}e$.

A quick way to remember the sign: up, charm and top sound positive, and their charge is positive, $+\tfrac{2}{3}e$. down, strange and bottom sound negative or low, and their charge is negative, $-\tfrac{1}{3}e$. This gives you the sign; the positive quarks are all $+\tfrac{2}{3}e$ and the negative quarks are all $-\tfrac{1}{3}e$.

• Every quark has an antiquark with the opposite sign. An anti-up is $-\tfrac{2}{3}e$, and an anti-down is $+\tfrac{1}{3}e$.