Long-exposure NuSTAR constraints on decaying dark matter in the Galactic halo

Brandon M. Roach, Steven Rossland, Kenny C. Y. Ng, Kerstin Perez, John F. Beacom, Brian W. Grefenstette, Shunsaku Horiuchi, Roman Krivonos, and Daniel R. Wik
Phys. Rev. D 107, 023009 – Published 13 January 2023

Abstract

We present two complementary NuSTAR x-ray searches for keV-scale dark matter decaying to monoenergetic photons in the Milky Way halo. In the first, we utilize the known intensity pattern of unfocused stray light across the detector planes—the dominant source of photons from diffuse sources—to separate astrophysical emission from internal instrument backgrounds using 7- Ms/detector deep blank-sky exposures. In the second, we present an updated parametric model of the full NuSTAR instrument background, allowing us to leverage the statistical power of an independent 20-Ms/detector stacked exposures spread across the sky. Finding no evidence of anomalous x-ray lines using either method, we set limits on the active-sterile mixing angle sin2(2θ) for sterile-neutrino masses 6–40 keV. The first key result is that we strongly disfavor a 7-keV sterile neutrino decaying into a 3.5-keV photon. The second is that we derive leading limits on sterile neutrinos with masses 1518keV and 2540keV, reaching or extending below the big bang nucleosynthesis limit. In combination with previous results, the parameter space for the neutrino minimal standard model is now nearly closed.

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  • Received 18 August 2022
  • Accepted 16 December 2022

DOI:https://doi.org/10.1103/PhysRevD.107.023009

© 2023 American Physical Society

Physics Subject Headings (PhySH)

Particles & FieldsGravitation, Cosmology & Astrophysics

Authors & Affiliations

Brandon M. Roach1,*, Steven Rossland2,†, Kenny C. Y. Ng3,‡, Kerstin Perez1,§, John F. Beacom4,5,6,∥, Brian W. Grefenstette7,¶, Shunsaku Horiuchi8,9,**, Roman Krivonos10,11,††, and Daniel R. Wik2,‡‡

  • 1Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
  • 2Department of Physics and Astronomy, University of Utah, Salt Lake City, Utah 84112, USA
  • 3Department of Physics, The Chinese University of Hong Kong, Sha Tin, Hong Kong, China
  • 4Center for Cosmology and AstroParticle Physics (CCAPP), Ohio State University, Columbus, Ohio 43210, USA
  • 5Department of Physics, Ohio State University, Columbus, Ohio 43210, USA
  • 6Department of Astronomy, Ohio State University, Columbus, Ohio 43210, USA
  • 7Space Radiation Laboratory, California Institute of Technology, Pasadena, California 91125, USA
  • 8Center for Neutrino Physics, Department of Physics, Virginia Tech, Blacksburg, Virginia 24061, USA
  • 9Kavli IPMU (WPI), UTIAS, The University of Tokyo, Kashiwa, Chiba 277-8583, Japan
  • 10Space Research Institute (IKI), Russian Academy of Sciences, Moscow 117997, Russia
  • 11Institute for Nuclear Research, Russian Academy of Sciences, Moscow 117312, Russia

  • *roachb@mit.edu
  • u1019304@utah.edu
  • kcyng@phy.cuhk.edu.hk
  • §kmperez@mit.edu
  • beacom.7@osu.edu
  • bwgref@srl.caltech.edu
  • **horiuchi@vt.edu
  • ††krivonos@cosmos.ru
  • ‡‡wik@astro.utah.edu

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Vol. 107, Iss. 2 — 15 January 2023

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