skip to main content
DOE PAGES title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Diffusion-limited relic particle production

Abstract

We examine the thermal evolution of particle number densities in the early universe when the particles have a finite diffusion length. Assuming that annihilations are impossible when the mean separation of the particles is larger than their diffusion length, we derive a version of the Boltzmann equation for freeze out in this scenario and an approximate solution, accurate to better than 2%. The effect of a finite diffusion length is to increase the final relic freeze-out abundance over its corresponding value when diffusion effects are ignored. When diffusion is limited only by scattering off of the thermal background, and the annihilation cross section is bounded by unitarity, a significant effect on the freeze-out abundance requires a scattering cross section much larger than the annihilation cross section. A similar effect is demonstrated when the relic particles are produced via the freeze-in mechanism, but in this case the finite diffusion length is due to the scattering of particles that annihilate into the relic particle of interest. For freeze in, the effect of a finite diffusion length is to reduce the final relic particle abundance. The effects of a finite diffusion length are most important when the scattering cross section or the relicmore » mass are very large. While we have not found a particularly compelling example where this would affect previous results, with the current interest in new dark matter candidates it could become an important consideration.« less

Authors:
ORCiD logo [1];  [2]
  1. Vanderbilt Univ., Nashville, TN (United States)
  2. Univ. of Chicago, IL (United States). Kavli Inst. for Cosmological Physics (KICP); Univ. of Chicago, IL (United States)
Publication Date:
Research Org.:
Vanderbilt Univ., Nashville, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC), High Energy Physics (HEP)
OSTI Identifier:
1599596
Alternate Identifier(s):
OSTI ID: 1566216
Grant/Contract Number:  
SC0019207
Resource Type:
Accepted Manuscript
Journal Name:
Physical Review D
Additional Journal Information:
Journal Volume: 100; Journal Issue: 4; Journal ID: ISSN 2470-0010
Publisher:
American Physical Society (APS)
Country of Publication:
United States
Language:
English
Subject:
79 ASTRONOMY AND ASTROPHYSICS; dark matter; relic particle abundances

Citation Formats

Scherrer, Robert J., and Turner, Michael S. Diffusion-limited relic particle production. United States: N. p., 2019. Web. https://doi.org/10.1103/PhysRevD.100.043545.
Scherrer, Robert J., & Turner, Michael S. Diffusion-limited relic particle production. United States. https://doi.org/10.1103/PhysRevD.100.043545
Scherrer, Robert J., and Turner, Michael S. Fri . "Diffusion-limited relic particle production". United States. https://doi.org/10.1103/PhysRevD.100.043545. https://www.osti.gov/servlets/purl/1599596.
@article{osti_1599596,
title = {Diffusion-limited relic particle production},
author = {Scherrer, Robert J. and Turner, Michael S.},
abstractNote = {We examine the thermal evolution of particle number densities in the early universe when the particles have a finite diffusion length. Assuming that annihilations are impossible when the mean separation of the particles is larger than their diffusion length, we derive a version of the Boltzmann equation for freeze out in this scenario and an approximate solution, accurate to better than 2%. The effect of a finite diffusion length is to increase the final relic freeze-out abundance over its corresponding value when diffusion effects are ignored. When diffusion is limited only by scattering off of the thermal background, and the annihilation cross section is bounded by unitarity, a significant effect on the freeze-out abundance requires a scattering cross section much larger than the annihilation cross section. A similar effect is demonstrated when the relic particles are produced via the freeze-in mechanism, but in this case the finite diffusion length is due to the scattering of particles that annihilate into the relic particle of interest. For freeze in, the effect of a finite diffusion length is to reduce the final relic particle abundance. The effects of a finite diffusion length are most important when the scattering cross section or the relic mass are very large. While we have not found a particularly compelling example where this would affect previous results, with the current interest in new dark matter candidates it could become an important consideration.},
doi = {10.1103/PhysRevD.100.043545},
journal = {Physical Review D},
number = 4,
volume = 100,
place = {United States},
year = {2019},
month = {8}
}

Works referenced in this record:

Symmetry Between Particle and Antiparticle Populations in the Universe
journal, September 1966


Cosmological Upper Bound on Heavy-Neutrino Lifetimes
journal, July 1977


Cosmology Confronts Particle Physics
journal, December 1979


On the relic, cosmic abundance of stable, weakly interacting massive particles
journal, March 1986


Unitarity limits on the mass and radius of dark-matter particles
journal, February 1990


Three exceptions in the calculation of relic abundances
journal, May 1991


Cosmic abundances of stable particles: Improved analysis
journal, August 1991


Precise relic WIMP abundance and its impact on searches for dark matter annihilation
journal, July 2012


Asymptotic analysis of the Boltzmann equation for dark matter relics in the presence of a running dilaton and space-time defects
journal, March 2013


Exact theory of freeze-out
journal, March 2015


On the concentration of relic magnetic monopoles in the universe
journal, November 1978


Particle–antiparticle annihilation in diffusive motion
journal, March 1983

  • Toussaint, Doug; Wilczek, Frank
  • The Journal of Chemical Physics, Vol. 78, Issue 5
  • DOI: 10.1063/1.445022

Density fluctuations and particle-antiparticle annihilation
journal, November 1984


Kinetic decoupling of neutralino dark matter
journal, June 2001


Thermal decoupling of WIMPs from first principles
journal, April 2007


Thermal relic abundances of particles with velocity-dependent interactions
journal, April 2010


Kinetic decoupling of WIMPs: Analytic expressions
journal, April 2015


Suppressing structure formation at dwarf galaxy scales and below: Late kinetic decoupling as a compelling alternative to warm dark matter
journal, November 2016


Late kinetic decoupling of light magnetic dipole dark matter
journal, June 2016


Quasidecoupled state for dark matter in nonstandard thermal histories
journal, June 2017


Dark matter kinetic decoupling with a light particle
journal, January 2018


Superheavy thermal dark matter and primordial asymmetries
journal, February 2017


Freeze-in production of FIMP dark matter
journal, March 2010

  • Hall, Lawrence J.; Jedamzik, Karsten; March-Russell, John
  • Journal of High Energy Physics, Vol. 2010, Issue 3
  • DOI: 10.1007/JHEP03(2010)080