Gamma-ray lines in 15 years of Fermi-LAT data: New constraints on Higgs portal dark matter

Letter
Open Access

Gamma-ray lines in 15 years of Fermi-LAT data: New constraints on Higgs portal dark matter

Pedro De La Torre Luque, Juri Smirnov, and Tim Linden

Phys. Rev. D 109, L041301 – Published 1 February 2024

Abstract

Monoenergetic $γ$ -ray spectral lines are among the cleanest signatures of dark matter annihilation. We analyze 15 years of Fermi-LAT data, find no spectral lines, and place strong constraints on dark matter annihilation to monoenergetic $γ$ -rays. Additionally, we produce the first double-line analysis of the coupled signals from $γ γ$ and $Z γ$ lines, which proves particularly powerful for dark matter masses above $\sim 150 GeV$ . From our constraints on a double-line feature, we investigate and constrain some minimal models where the Galactic Center Excess can be fit by dark matter annihilation through the Higgs boson into Standard Model particles.

Received 25 September 2023
Accepted 8 January 2024

DOI:https://doi.org/10.1103/PhysRevD.109.L041301

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)

Dark matter Evolution of the Universe Gamma ray astronomy

Gravitation, Cosmology & Astrophysics

Authors & Affiliations

Pedro De La Torre Luque ^1,2,*, Juri Smirnov^3,1,†, and Tim Linden ^1,‡

¹Stockholm University and The Oskar Klein Centre for Cosmoparticle Physics, Alba Nova, 10691 Stockholm, Sweden
²Polytechnic School, Universidad San Pablo-CEU, CEU Universities, 28668 Boadilla del Monte, Spain
³Department of Mathematical Sciences, University of Liverpool, Liverpool L69 7ZL, United Kingdom

^*pedro.delatorreluque@fysik.su.se
^†juri.smirnov@liverpool.ac.uk
^‡linden@fysik.su.se

Article Text

Click to Expand

Supplemental Material

Click to Expand

References

Click to Expand

Issue

Vol. 109, Iss. 4 — 15 February 2024

Reuse & Permissions

Author publication services for translation and copyediting assistance advertisement

Images

Figure 1
The results of our model-independent single-line (blue solid) and Higgs portal double-line (red solid) analysis, given an NFW profile in ROI41. Single-line analyses by the Fermi-LAT Collaboration (2015) [24] (gray solid) and a recent result by Ref. [25] (magenta dashed) are shown for comparison.
Reuse & Permissions
Figure 2
Local significance obtained in the 10 to 300 GeV range. We compare the result of the single-line analysis (solid lines) and double-line analysis (dashed lines) for each ROI: 3° (upper), 16° (middle), and 41° (lower) around the center of the Galaxy. For those signals where there is no preference for a positive number of counts over the background, the significance ( $σ_{local}$ ) is set to 0.
Reuse & Permissions
Figure 3
DM bounds for the ROI41 region assuming a NFW Galactic DM profile, including the 68% and 95% confidence intervals obtained from the single-line analysis, compared to those obtained in the double-line analysis, as a solid line and a dashed line, respectively.
Reuse & Permissions
Figure 4
The Higgs portal total annihilation rate as a function of the DM mass. We superimpose our constraint from the double-line analysis on the total annihilation rate using the branching ratio $Br (h \to γ, γ)$ for the conversion (red solid). Additionally, we show the dwarf spheroidal limits from the Fermi-LAT Collaboration [57] (green solid), which are dominated by the $b \bar{b}$ channel in the Higgs portal model in the relevant mass range [50]. The constraints from invisible Higgs decay searches [55] are shown as the gray contour. The rate factor predicted by the relic density constraint is shown as a function of DM mass (black dashed). Additionally, we include (gray dashed line) the relic density rate as computed from the DRAKE code [58], taken from Ref. [59]. Two scenarios of the QCD phase transition are taken into account indicated by the doubling of the relic density line in the resonant region. Finally, the blue ellipse shows the 95% confidence interval for the GCE from Ref. [60].
Reuse & Permissions
Figure 5
The predictions for the $γ γ$ (dark red) and $Z γ$ (magenta) annihilation rates in the Higgs portal model, calculated given the GCE 95% confidence interval found in Ref. [60] for the best-fit DM mass and coupling strength based on the fit to the dominant $b \bar{b}$ channel. We superimpose our double-line search limits from a gNFW profile in ROI41 (red solid), and the $⟨ σ v ⟩_{γ γ}$ values predicted by the freeze-out (black dashed). Note that in contrast to constraints from dwarf galaxies this search for $γ$ -lines in the GC does not have an intrinsic J-factor uncertainty, when the comparison to the continuum excess is made.
Reuse & Permissions

Physical Review D

covering particles, fields, gravitation, and cosmology