Properties of Quarks (Cambridge (CIE) AS Physics): Revision Note

Particles are made up of a combination of three quarks or two quarks. Which quark combination would not give a particle a charge of -1 or 0?

A. up, strange, strange

B. charm, charm, down

C. top, anti-up

D. anti-up, anti-up, anti-strange

Answer: B

• Add up the charge of the individual quarks

  • Charm, charm, down = $\frac{2}{3}+\frac{2}{3}-\frac{1}{3}=+1$

• The other quark combinations add up to either 0 or −1

  • A: Up, strange, strange = $\frac{2}{3}-\frac{1}{3}-\frac{1}{3}=0$

  • C: Top, anti-up = $+\frac{2}{3}-\frac{2}{3}=0$

  • D: Anti-up, anti-up, anti-strange $-\frac{2}{3}-\frac{2}{3}+\frac{1}{3}=-1$

    • Remember that anti-particles have the opposite signs

You will be expected to remember the charge of each quark. However, instead of memorising the charges of anti-quarks too, just remember they are identical but with opposite signs.