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Nuclear and Particle Physics

Baryons, mesons, leptons and quark composition

  • 3 things to know
  • Papers 1 and 3

Overview

Recall questions on the four classes of particle, what a baryon, meson and lepton are, and the quark compositions of the proton, the neutron and the pions.

What you need to know

Answer each one before you reveal it.

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Key term

What are a meson and a lepton, and what collective name is given to particles built from quarks?

Key term

What are the quark compositions of a proton and a neutron, and what are the charges of the up and down quarks?

Numbers

How do the quark compositions of a proton, a neutron and a positive pion give their charges?

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    Into which four classes are particles placed in the standard quark-lepton model?

    Model answer

    Particles are classified as baryons, mesons, leptons and photons.

  2. 2

    What is a baryon?

    Model answer

    A baryon is a particle made from three quarks, such as a proton or a neutron.

  3. 3

    What is a meson?

    Model answer

    A meson is a particle made from one quark and one antiquark, such as a pion.

  4. 4

    What is a lepton?

    Model answer

    A lepton is a fundamental particle that is not made of quarks, such as an electron or a neutrino.

  5. 5

    What collective name is given to particles built from quarks?

    Model answer

    They are called hadrons, a group that includes both the baryons and the mesons.

  6. 6

    What is the quark composition of a proton?

    Model answer

    A proton consists of two up quarks and one down quark, uud.

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