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Fundamental Particles

Beta decay in the quark model

  • 3 things to know
  • Unit A2 2

Overview

Beta-minus decay at the quark level and beta-plus decay at the quark level.

What you need to know

Answer each one before you reveal it.

Your recallNot started
Key term

What happens in beta-minus decay, at the level of the particles and at the level of the quarks?

Key term

Write the equation for beta-minus decay of a neutron.

Key term

Describe beta-minus decay at the quark level.

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    Write the equation for beta-minus decay of a neutron.

    Model answer

    n → p + e⁻ + ν̄ₑ, a neutron becoming a proton with the emission of an electron and an electron antineutrino.

  2. 2

    Describe beta-minus decay at the quark level.

    Model answer

    A down quark in the neutron changes into an up quark, emitting an electron and an electron antineutrino.

  3. 3

    Write the quark equation for beta-minus decay.

    Model answer

    d → u + e⁻ + ν̄ₑ.

  4. 4

    Show that the quark change turns a neutron into a proton.

    Model answer

    The neutron is udd, and changing one down quark to an up quark gives uud, which is the proton.

  5. 5

    Which exchange particle mediates beta-minus decay?

    Model answer

    The W⁻ boson, emitted by the down quark as it becomes an up quark and then decaying into the electron and the antineutrino.

  6. 6

    Write the equation for beta-plus decay.

    Model answer

    p → n + e⁺ + νₑ, a proton becoming a neutron with the emission of a positron and an electron neutrino.

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