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5.3.2 Fundamental Particles. (a) explain that since protons and neutrons contain charged constituents called quarks they are, therefore, not fundamental particles. Fundamental particles. Until mid-20 th century, it was though that all atoms consisted of electrons, protons and neutrons

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5 3 2 fundamental particles

(a) explain that since protons and neutrons contain charged constituents called quarks they are, therefore, not fundamental particles


Fundamental particles
Fundamental particles constituents called quarks they are, therefore, not fundamental particles

  • Until mid-20th century, it was though that all atoms consisted of electrons, protons and neutrons

  • Due to the increasing sophistication of the particle accelerator, and increased sensitivity of equipment measuring cosmic rays, more and more particles were being discovered

  • Eventually, this “particle zoo” was arranged in a more orderly way


Video
Video constituents called quarks they are, therefore, not fundamental particles

Fundamental Particles

CERN Standard model


5 3 2 fundamental particles

(b) describe a simple quark model of hadrons in terms of up, down and strange quarks and their respective antiquarks, taking into account their charge, baryon number and strangeness;


Simple model
Simple model down and strange quarks and their respective

Atom

Hadrons

Leptons

Not affected by the strong nuclear force

Affected by the strong nuclear force

Electrons

Neutrinos

Protons

Neutrons

Quarks


Fermions
Fermions down and strange quarks and their respective



Properties of neutrons and protons
Properties of neutrons and protons of a simple quark model

Proton

Neutron

u d d

u u d


Properties of neutrons and protons1
Properties of neutrons and protons of a simple quark model

  • Proton

    • uud

    • total charge = ⅔ + ⅔ - ⅓ = 1

  • Neutron

    • udd

    • total charge = ⅔ - ⅓ - ⅓ = 0


E describe how there is a weak interaction between quarks and that this is responsible for decay

(e) of a simple quark modeldescribe how there is a weak interaction between quarks and that this is responsible for β decay


Decay
β of a simple quark modeldecay

  • Nucleus is held together by the strong nuclear force

  • This explains α decay, but not β decay

  • There is another force, the weak interaction or weak nuclear force

  • Acts on quarks and leptons

  • Responsible for β decay


5 3 2 fundamental particles

(f) of a simple quark modelstate that there are two types of β decay

(i) state that a β- particle is an electron and a β+particle is a positron


Decay1
β of a simple quark modeldecay

  • There are two types of β decay:

  • Beta-minus (β-)

    • electron

    • negative charge –e

  • Beta-plus (β+)

    • positron

    • positive charge +e


5 3 2 fundamental particles

(g) of a simple quark modeldescribe the two types of β decay in terms of a simple quark model;

(h) state that (electron) neutrinos and electron) antineutrinos are produced during β+ and β-decays, respectively


Decay2
β of a simple quark model-decay

Electron

Anti-neutrino

In β- decay a neutron is changed into a proton, in other words uddchanges into uud. A d changing to a u can only happen through the weak interaction.


Decay3
β of a simple quark model+decay

Electron

neutrino

In β+ decay a proton is changed into a neutron, in other words uudchanges into udd. A u changing to a d can only happen through the weak interaction.