Electron-Positron Annihilation Freeze-Out in the Early Universe
arXiv:1910.14050 · doi:10.1103/PhysRevD.101.063507
Abstract
Electron-positron annihilation largely occurs in local thermal and chemical equilibrium after the neutrinos fall out of thermal equilibrium and during the Big Bang Nucleosynthesis (BBN) epoch. The effects of this process are evident in BBN yields as well as the relativistic degrees of freedom. We self-consistently calculate the collision integral for electron-positron creation and annihilation using the Klein-Nishina amplitude and appropriate statistical factors for Fermi-blocking and Bose-enhancement. Our calculations suggest that this annihilation freezes out when the photon-electron-positron-baryon plasma temperature is approximately 16 keV, after which its rate drops below the Hubble rate. In the temperature regime near 16 keV, we break the assumption of chemical equilibrium between the electrons, positrons, and photons to independently calculate the evolution of the chemical potentials of the electrons and positrons while computing the associated collision integrals at every time step. We find that the electron and positron chemical potentials deviate from the case with chemical equilibrium. While our results do not affect the interpretation of precision cosmological measurements in elucidating the standard cosmological model, these out of equilibrium effects may be important for testing physics beyond the standard model.
References in corpus (25)
- Planck 2015 results. XIII. Cosmological parameters
- Big-Bang Nucleosynthesis and Hadronic Decay of Long-Lived Massive Particles
- Relic neutrino decoupling including flavour oscillations
- Big Bang Nucleosynthesis Constraints on Hadronically and Electromagnetically Decaying Relic Neutral Particles
- Precision big bang nucleosynthesis with improved Helium-4 predictions
- Cosmological bounds on neutrino degeneracy improved by flavor oscillations
- Relic neutrino decoupling with flavour oscillations revisited
- A precision calculation of the effective number of cosmological neutrinos
- Revisiting Big-Bang Nucleosynthesis Constraints on Long-Lived Decaying Particles
- Nonequilibrium Corrections to the Spectra of Massless Neutrinos in the Early Universe
- Big Bang Nucleosynthesis and Particle Dark Matter
- Cosmological Constraints on Very Dark Photons
- Neutrino energy transport in weak decoupling and big bang nucleosynthesis
- PArthENoPE reloaded
- Primordial nucleosynthesis as a probe of fundamental physics parameters
- Nucleosynthesis and the variation of fundamental couplings
- Sterile Neutrinos with Secret Interactions -- Cosmological Discord?
- Cosmological Constraints on Decoupled Dark Photons and Dark Higgs
- Relic Neutrino Freeze-out: Dependence on Natural Constants
- Revisiting Big-Bang Nucleosynthesis Constraints on Dark-Matter Annihilation
- Is Self-Interacting Dark Matter Undergoing Dark Fusion?
- Lepton asymmetry, neutrino spectral distortions, and big bang nucleosynthesis
- Probing neutrino physics with a self-consistent treatment of the weak decoupling, nucleosynthesis, and photon decoupling epochs
- The surprising influence of late charged current weak interactions on Big Bang Nucleosynthesis
- Insights into neutrino decoupling gleaned from considerations of the role of electron mass