5 3 2 fundamental particles
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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

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5 3 2 fundamental particles

5.3.2 Fundamental Particles


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

  • 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

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

Atom

Hadrons

Leptons

Not affected by the strong nuclear force

Affected by the strong nuclear force

Electrons

Neutrinos

Protons

Neutrons

Quarks


Fermions

Fermions


D describe the properties of neutrons and protons in terms of a simple quark model

(d) describe the properties of neutrons and protons in terms of a simple quark model


Properties of neutrons and protons

Properties of neutrons and protons

Proton

Neutron

u d d

u u d


Properties of neutrons and protons1

Properties of neutrons and protons

  • 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) describe how there is a weak interaction between quarks and that this is responsible for β decay


Decay

β decay

  • 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) state 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 decay

  • 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) describe 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-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+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.


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