Effect of neutrino rest mass on ionization equilibrium freeze-out

Journal Article · Wed Dec 23 00:00:00 EST 2015 · Physical Review. D, Particles, Fields, Gravitation and Cosmology

DOI:https://doi.org/10.1103/PhysRevD.92.125027· OSTI ID:1248609

Grohs, Evan Bradley ^[1]; Fuller, George M. ^[1]; Kishimoto, Chad T. ^[2]; Paris, Mark W. ^[3]

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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

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.

• Research Organization: Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA)
• Grant/Contract Number: PHY-1307372; 257842; AC52-06NA25396
• OSTI ID: 1248609
• Alternate ID(s): OSTI ID: 1233889
• Report Number(s): LA-UR-14-29625; PRVDAQ
• Journal Information: Physical Review. D, Particles, Fields, Gravitation and Cosmology, Vol. 92, Issue 12; ISSN 1550-7998
• Publisher: American Physical Society (APS)
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS