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Title: Effect of neutrino rest mass on ionization equilibrium freeze-out

We show how small neutrino rest masses can increase the expansion rate near the photon decoupling epoch in the early Universe, causing an earlier, higher temperature freeze-out for ionization equilibrium compared to the massless neutrino case. This yields a larger free-electron fraction, thereby affecting the photon diffusion length differently than the sound horizon at photon decoupling. This neutrino-mass and recombination effect depends strongly on the neutrino rest masses. Ultimately, though below current sensitivity, this effect could be probed by next-generation cosmic microwave background experiments, giving another observational handle on neutrino rest mass.
Authors:
 [1] ;  [1] ;  [2] ;  [3]
  1. Univ. of California, San Diego, CA (United States). Dept. of Physics
  2. Univ. of California, San Diego, CA (United States). Dept. of Physics; Univ. of San Diego, San Diego, CA (United States)
  3. Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Theoretical Division
Publication Date:
OSTI Identifier:
1248609
Report Number(s):
LA-UR--14-29625
Journal ID: ISSN 1550-7998; PRVDAQ
Grant/Contract Number:
PHY-1307372; 257842; AC52-06NA25396
Type:
Accepted Manuscript
Journal Name:
Physical Review. D, Particles, Fields, Gravitation and Cosmology
Additional Journal Information:
Journal Volume: 92; Journal Issue: 12; Journal ID: ISSN 1550-7998
Publisher:
American Physical Society (APS)
Research Org:
Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
Sponsoring Org:
USDOE National Nuclear Security Administration (NNSA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTRONOMY AND ASTROPHYSICS; 73 NUCLEAR PHYSICS AND RADIATION PHYSICS; 72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS