• Open Access

Cosmological constraints on unstable particles: Numerical bounds and analytic approximations

Keith R. Dienes, Jason Kumar, Patrick Stengel, and Brooks Thomas
Phys. Rev. D 99, 043513 – Published 12 February 2019

Abstract

Many extensions of the Standard Model predict large numbers of additional unstable particles whose decays in the early universe are tightly constrained by observational data. For example, the decays of such particles can alter the ratios of light-element abundances, give rise to distortions in the cosmic microwave background, alter the ionization history of the Universe, and contribute to the diffuse photon flux. Constraints on new physics from such considerations are typically derived for a single unstable particle species with a single well-defined mass and characteristic lifetime. In this paper, by contrast, we investigate the cosmological constraints on theories involving entire ensembles of decaying particles—ensembles which span potentially broad ranges of masses and lifetimes. In addition to providing a detailed numerical analysis of these constraints, we also formulate a set of simple analytic approximations for these constraints which may be applied to generic ensembles of unstable particles which decay into electromagnetically interacting final states. We then illustrate how these analytic approximations can be used to constrain a variety of toy scenarios for physics beyond the Standard Model. For ease of reference, we also compile our results in the form of a table which can be consulted independently of the rest of the paper. It is thus our hope that this work might serve as a useful reference for future model-builders concerned with cosmological constraints on decaying particles, regardless of the particular model under study.

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  • Received 16 November 2018

DOI:https://doi.org/10.1103/PhysRevD.99.043513

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP3.

Published by the American Physical Society

Physics Subject Headings (PhySH)

Gravitation, Cosmology & Astrophysics

Authors & Affiliations

Keith R. Dienes1,2,*, Jason Kumar3,†, Patrick Stengel4,5,‡, and Brooks Thomas6,§

  • 1Department of Physics, University of Arizona, Tucson, Arizona 85721 USA
  • 2Department of Physics, University of Maryland, College Park, Maryland 20742 USA
  • 3Department of Physics and Astronomy, University of Hawaii, Honolulu, Hawaii 96822 USA
  • 4Leinweber Center for Theoretical Physics, Department of Physics, University of Michigan, Ann Arbor, Michigan 48109 USA
  • 5Oskar Klein Centre for Cosmoparticle Physics, Department of Physics, Stockholm University, Alba Nova, 10691 Stockholm, Sweden
  • 6Department of Physics, Lafayette College, Easton, Pennsylvania 18042 USA

  • *dienes@email.arizona.edu
  • jkumar@hawaii.edu
  • patrick.stengel@fysik.su.se
  • §thomasbd@lafayette.edu

Article Text

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Issue

Vol. 99, Iss. 4 — 15 February 2019

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