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<p>We explore the indirect detection of sterile neutrino dark matter within the gauged U(1)<sub>B<i>−</i>L</sub> extension of the Standard Model, in which three right-handed neutrinos account for neutrino masses, the baryon asymmetry, and dark matter. Focusing on the MeV mass range, we investigate two decay channels: the radiative decay <i>N</i> → <i>νγ</i>, which produces a monochromatic photon, and the three-body decay <i>N</i> → <i>e</i><sup><i>−</i></sup><i>e</i><sup>+</sup><i>ν</i>, which leads to a 511 keV photon signal from positronium decay. Taking the upcoming COSI mission as a case study, we show that both signals are experimentally accessible and complementary, with the 511 keV channel extending the sensitivity reach up to <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(\mathcal{O}(100)\)</EquationSource> </InlineEquation> MeV. We propose a novel analysis strategy in Compton data space to isolate the diffuse 511 keV emission. Furthermore, we incorporate, for the first time, the Sommerfeld enhancement in the decay width of <i>N</i> → <i>e</i><sup><i>−</i></sup><i>e</i><sup>+</sup><i>ν</i>, enabling more accurate predictions of the signal near the kinematic threshold. The combined observation of both channels would provide a distinctive and testable signature of the sterile neutrino dark matter hypothesis.</p>

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Detecting sterile neutrino dark matter at MeV gamma-ray observatories

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年1月15日

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  • Subaru Fujisawa,
  • Tatsuya Hayashi,
  • Shigeki Matsumoto,
  • Yuki Watanabe

摘要

We explore the indirect detection of sterile neutrino dark matter within the gauged U(1)B−L extension of the Standard Model, in which three right-handed neutrinos account for neutrino masses, the baryon asymmetry, and dark matter. Focusing on the MeV mass range, we investigate two decay channels: the radiative decay N → νγ, which produces a monochromatic photon, and the three-body decay N → e−e+ν, which leads to a 511 keV photon signal from positronium decay. Taking the upcoming COSI mission as a case study, we show that both signals are experimentally accessible and complementary, with the 511 keV channel extending the sensitivity reach up to \(\mathcal{O}(100)\) MeV. We propose a novel analysis strategy in Compton data space to isolate the diffuse 511 keV emission. Furthermore, we incorporate, for the first time, the Sommerfeld enhancement in the decay width of N → e−e+ν, enabling more accurate predictions of the signal near the kinematic threshold. The combined observation of both channels would provide a distinctive and testable signature of the sterile neutrino dark matter hypothesis.