Particle Zoo

What is the baryon number of a down quark?

What is the lepton number of an electron-neutrino?

What is the charge of an up quark?

What is the baryon number of the anti-electron neutrino?

How many of the fundamental particles of the standard model have zero mass?

Answer explanation

The photon and the gluon are the only fundamental particles that have zero mass. The mass of the neutrinos is very small indeed, but non-zero.

Which of the following statements is false?

• All particles made of quarks are called hadrons.

Answer explanation

Pions are made mesons (made of a quark antiquark pair) and they are made exclusively with u and d quarks

What is the strangeness of a strange quark?

Answer explanation

The strangeness of a strange quark is -1 and the strangeness of an anti-strange quark is +1. Strange, isn't it? All other particles have zero strangeness.

Which one of these is an exchange boson that mediates the weak interaction?

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Answer explanation

The weak interaction is mediated by the w-minus, W-plus, and Z-zero particles.

Which one of these is an exchange boson that mediates the strong interaction?

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Answer explanation

The strong force between quarks is mediated by the gluon, but between nucleons (in a nucleus) the strong interaction is mediation by virtual pion exchange.