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Title: What does the PAMELA antiproton spectrum tell us about dark matter?

Abstract

Measurements of the cosmic ray antiproton spectrum can be used to search for contributions from annihilating dark matter and to constrain the dark matter annihilation cross section. Depending on the assumptions made regarding cosmic ray propagation in the Galaxy, such constraints can be quite stringent. We revisit this topic, utilizing a set of propagation models fit to the cosmic ray boron, carbon, oxygen and beryllium data. We derive upper limits on the dark matter annihilation cross section and find that when the cosmic ray propagation parameters are treated as nuisance parameters (as we argue is appropriate), the resulting limits are significantly less stringent than have been previously reported. We also note (as have several previous groups) that simple GALPROP-like diffusion-reacceleration models predict a spectrum of cosmic ray antiprotons that is in good agreement with PAMELA's observations above ∼ 5 GeV, but that significantly underpredict the flux at lower energies. Although the complexity of modeling cosmic ray propagation at GeV-scale energies makes it difficult to determine the origin of this discrepancy, we consider the possibility that the excess antiprotons are the result of annihilating dark matter. Suggestively, we find that this excess is best fit for m{sub DM} ∼ 35 GeV andmore » σ v ∼ 10{sup −26} cm{sup 3}/s (to b b-bar ), in good agreement with the mass and cross section previously shown to be required to generate the gamma-ray excess observed from the Galactic Center.« less

Authors:
 [1];  [2];  [3]
  1. Center for Particle Astrophysics, Fermi National Accelerator Laboratory, P.O. Box 500, Batavia, IL (United States)
  2. Kavli Institute for Cosmological Physics, University of Chicago, 5640 S. Ellis Ave., Chicago, IL (United States)
  3. Kavli Insitute for Particle Astrophysics and Cosmology, Stanford University, 2575 Sand Hill Rd., Menlo Park, CA (United States)
Publication Date:
OSTI Identifier:
22524865
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Cosmology and Astroparticle Physics; Journal Volume: 2015; Journal Issue: 03; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ANNIHILATION; ANTIPROTONS; BERYLLIUM; BORON; CARBON; COSMIC RADIATION; COSMIC RAY PROPAGATION; CROSS SECTIONS; DIFFUSION; GALAXIES; GAMMA RADIATION; GEV RANGE; LIMITING VALUES; MASS; NONLUMINOUS MATTER; OXYGEN

Citation Formats

Hooper, Dan, Linden, Tim, and Mertsch, Philipp, E-mail: dhooper@fnal.gov, E-mail: trlinden@uchicago.edu, E-mail: pmertsch@stanford.edu. What does the PAMELA antiproton spectrum tell us about dark matter?. United States: N. p., 2015. Web. doi:10.1088/1475-7516/2015/03/021.
Hooper, Dan, Linden, Tim, & Mertsch, Philipp, E-mail: dhooper@fnal.gov, E-mail: trlinden@uchicago.edu, E-mail: pmertsch@stanford.edu. What does the PAMELA antiproton spectrum tell us about dark matter?. United States. doi:10.1088/1475-7516/2015/03/021.
Hooper, Dan, Linden, Tim, and Mertsch, Philipp, E-mail: dhooper@fnal.gov, E-mail: trlinden@uchicago.edu, E-mail: pmertsch@stanford.edu. Sun . "What does the PAMELA antiproton spectrum tell us about dark matter?". United States. doi:10.1088/1475-7516/2015/03/021.
@article{osti_22524865,
title = {What does the PAMELA antiproton spectrum tell us about dark matter?},
author = {Hooper, Dan and Linden, Tim and Mertsch, Philipp, E-mail: dhooper@fnal.gov, E-mail: trlinden@uchicago.edu, E-mail: pmertsch@stanford.edu},
abstractNote = {Measurements of the cosmic ray antiproton spectrum can be used to search for contributions from annihilating dark matter and to constrain the dark matter annihilation cross section. Depending on the assumptions made regarding cosmic ray propagation in the Galaxy, such constraints can be quite stringent. We revisit this topic, utilizing a set of propagation models fit to the cosmic ray boron, carbon, oxygen and beryllium data. We derive upper limits on the dark matter annihilation cross section and find that when the cosmic ray propagation parameters are treated as nuisance parameters (as we argue is appropriate), the resulting limits are significantly less stringent than have been previously reported. We also note (as have several previous groups) that simple GALPROP-like diffusion-reacceleration models predict a spectrum of cosmic ray antiprotons that is in good agreement with PAMELA's observations above ∼ 5 GeV, but that significantly underpredict the flux at lower energies. Although the complexity of modeling cosmic ray propagation at GeV-scale energies makes it difficult to determine the origin of this discrepancy, we consider the possibility that the excess antiprotons are the result of annihilating dark matter. Suggestively, we find that this excess is best fit for m{sub DM} ∼ 35 GeV and σ v ∼ 10{sup −26} cm{sup 3}/s (to b b-bar ), in good agreement with the mass and cross section previously shown to be required to generate the gamma-ray excess observed from the Galactic Center.},
doi = {10.1088/1475-7516/2015/03/021},
journal = {Journal of Cosmology and Astroparticle Physics},
number = 03,
volume = 2015,
place = {United States},
year = {Sun Mar 01 00:00:00 EST 2015},
month = {Sun Mar 01 00:00:00 EST 2015}
}