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.
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Particles

• This lecture
• Particles in the hot early universe

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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

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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

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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

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The standard model of particle physics

• Higgs boson
• Higgs q0 m 125 GeV

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Inflation is over

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

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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.

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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.

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• 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.