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Cosmology and extragalactic astronomy

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Cosmology and extragalactic astronomy Mat Page Mullard Space Science Lab, UCL Particles in the hot, early Universe. Particles This lecture: Particles in the hot early ... – PowerPoint PPT presentation

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Title: Cosmology and extragalactic astronomy


1
Cosmology and extragalactic astronomy
Mat Page
Mullard Space Science Lab, UCL
Particles in the hot, early Universe.
2
Particles
  • This lecture
  • Particles in the hot early universe

3
The standard model of particle physics
  • Leptons
  • electron q-1 m0.5 MeV
  • e-neutrino q0 mlt3 eV
  • muon q-1 m0.1 GeV
  • m-neutrino q0 mlt0.17 MeV
  • tau q-1 m1.8 GeV
  • tau-neutrino q0 mlt24 MeV

4
The standard model of particle physics
  • Quarks
  • up q2/3 m6 MeV
  • down q-1/3 m10 MeV
  • strange q-1/3 m0.25 GeV
  • charm q2/3 m1.2 GeV
  • bottom q-1/3 m4.3 GeV
  • top q2/3 m180 GeV

5
The standard model of particle physics
  • Vector bosons
  • photon q0 m0
  • W boson q-1 m80.3 GeV
  • Z boson q0 m91.2 GeV
  • gluon q0 m0

6
The standard model of particle physics
  • Higgs boson
  • Higgs q0 m 125 GeV

7
Inflation is over
  • The Universe is hot, and dominated by radiation.
  • Radiation and matter in equilibrium
  • pairs of hadrons or leptons lt gt radiation

8
Quarks
  • Quarks are fundamental particles which may be
    the building blocks of all the hadrons.
  • They have fractional charge
  • 1/3 or 2/3 of the electronic charge
  • 3 quarks make a proton, antiproton or neutron.

9
Free quarks
  • Quarks are only created at very high energies.
  • At 1013 K (109 eV) quark-antiquark pairs are
    created and annihilated just like electrons and
    positrons at 106 eV.
  • When the temperature drops, quark-antiquark pairs
    annihilate, but the photons dont have enough
    energy to make quark-antiquark pairs anymore.

10
  • Then the quarks combine to make stable baryons
  • quarks are effectively forbidden in coloured
    combinations
  • colour is a quantum number of quarks, like spin
    in electrons.
  • There are now virtually no free quarks
  • but the only way to destroy a quark is to
    annihilate it with an antiquark or combine it
    with other quarks - there could be a small number
    of free quarks hanging around with nowhere to go,
    relics of the primordial soup.
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