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Study Report. Particle Astrophysics D.H. PERKINS Chapter 2.10. Che -Yu Chen 2010-3-06. Primordial nucleosynthesis. Weak reactions in equilibrium Neutron decay The formation reaction begins. Weak reactions in equilibrium.

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study report

Study Report

Particle Astrophysics

D.H. PERKINS

Chapter 2.10

Che-Yu Chen

2010-3-06

primordial nucleosynthesis
Primordial nucleosynthesis
  • Weak reactions in equilibrium
  • Neutron decay
  • The formation reaction begins
weak reactions in equilibrium
Weak reactions in equilibrium
  • After baryogenesis, the neutrons and protons are in equilibrium by the weak reactions.
  • The ratio of neutrons and protons is determined by the Boltzmann factors.
neutron decay
Neutron decay
  • After the rate of these weak reactions becomes smaller than the universe expand rate, the reactions are ‘’freeze-out’’.
  • Accompanied with neutrino decoupling.
  • kT=0.80MeV
  • Mn(0)/Mp(0)=0.20
neutron decay1
Neutron decay
  • Neutrons disappear by decay
the formation reaction begins
The formation reaction begins
  • At kT=0.05MeV, nucleosynthesis can begin with the formation of deuterons:
  • It’s at t ~ 300s(derived from )
other reactions
Other reactions

There are no stable nuclei with A=5, 6 or 8 . The further formation has to await to the onset of helium burning in stars core.