scholarly journals Observational Constraints of 30–40 GeV Dark Matter Annihilation in Galaxy Clusters

2016 ◽  
Vol 2016 ◽  
pp. 1-4
Author(s):  
Man Ho Chan
Keyword(s):  
Dark Matter ◽  
Galaxy Clusters ◽  
Cross Section ◽  
Upper Bound ◽  
Gamma Ray ◽  
Galactic Center ◽  
Cosmic Ray ◽  
Annihilation Cross Section ◽  
Dark Matter Annihilation ◽  
The One

Recently, it has been shown that the annihilation of 30–40 GeV dark matter particles through bb- channel can satisfactorily explain the excess GeV gamma-ray spectrum near the Galactic Center. In this paper, we apply the above model to galaxy clusters and use the latest upper limits of gamma-ray flux derived from Fermi-LAT data to obtain an upper bound of the annihilation cross section of dark matter. By considering the extended density profiles and the cosmic ray profile models of 49 galaxy clusters, the upper bound of the annihilation cross section can be further tightened to σv≤9×10-26 cm3 s−1. This result is consistent with the one obtained from the data near the Galactic Center.

An excess radio signal in the Abell 4038 cluster

2020 ◽  
Vol 500 (4) ◽  
pp. 5583-5588
Author(s):  
Man Ho Chan ◽  
Chak Man Lee
Keyword(s):  
Dark Matter ◽  
Spectral Data ◽  
Cross Section ◽  
Radio Signal ◽  
Dark Matter Particle ◽  
Cosmic Ray ◽  
Annihilation Cross Section ◽  
Radio Continuum ◽  
Test Statistic ◽  
Dark Matter Annihilation

ABSTRACT In the past decade, various instruments, such as the Large Area Telescope (LAT) on the Fermi Gamma Ray Space Telescope, the Alpha Magnetic Spectrometer (AMS) and the Dark Matter Particle Explorer(DAMPE), have been used to detect the signals of annihilating dark matter in our Galaxy. Although some excesses of gamma rays, antiprotons and electrons/positrons have been reported and are claimed to be dark matter signals, the uncertainties of the contributions of Galactic pulsars are still too large to confirm the claims. In this paper, we report on a possible radio signal of annihilating dark matter manifested in the archival radio continuum spectral data of the Abell 4038 cluster. By assuming a thermal annihilation cross-section and comparing the dark matter annihilation model with the null hypothesis (cosmic ray emission without dark matter annihilation), we obtain very large test statistic (TS) values, TS > 45, for four popular annihilation channels, which correspond to more than 6σ statistical preference. This reveals a possible potential signal of annihilating dark matter. In particular, our results are also consistent with the recent claims of dark matter mass, m ≈ 30–50 GeV, annihilating via the $\rm b\bar{b}$ quark channel with the thermal annihilation cross-section. However, at this time, we cannot exclude the possibility that a better background cosmic ray model could explain the spectral data without recourse to dark matter annihilations.

scholarly journals A possible radio signal of annihilating dark matter in the Abell 4038 cluster

2019 ◽  
Vol 495 (1) ◽  
pp. L124-L128 ◽  
Author(s):  
Man Ho Chan ◽  
Chak Man Lee
Keyword(s):  
Dark Matter ◽  
Cross Section ◽  
Radio Signal ◽  
Dark Matter Particle ◽  
Cosmic Ray ◽  
Annihilation Cross Section ◽  
Radio Continuum ◽  
Test Statistic ◽  
Large Area ◽  
Dark Matter Annihilation

ABSTRACT In the past decade, some telescopes [e.g. Fermi-Large Area Telescope (LAT), Alpha Magnetic Spectrometer(AMS), and Dark Matter Particle Explorer(DAMPE)] were launched to detect the signals of annihilating dark matter in our Galaxy. Although some excess of gamma-rays, antiprotons, and electrons/positrons have been reported and claimed as dark matter signals, the uncertainties of Galactic pulsars’ contributions are still too large to confirm the claims. In this Letter, we report a possible radio signal of annihilating dark matter manifested in the archival radio continuum spectral data of the Abell 4038 cluster. By assuming the thermal annihilation cross-section and comparing the dark matter annihilation model with the null hypothesis (cosmic ray emission without dark matter annihilation), we get very large test statistic values >45 for four popular annihilation channels, which correspond to more than 6.5σ statistical preference. This provides a very strong evidence for the existence of annihilating dark matter. In particular, our results also support the recent claims of dark matter mass m ≈ 30–50 GeV annihilating via the bb̄ quark channel with the thermal annihilation cross-section.

scholarly journals Cosmic-ray positrons strongly constrain leptophilic dark matter

2021 ◽  
Vol 2021 (12) ◽  
pp. 007
Author(s):  
Isabelle John ◽  
Tim Linden
Keyword(s):  
Dark Matter ◽  
Cross Section ◽  
Cosmic Ray ◽  
Propagation Model ◽  
Annihilation Cross Section ◽  
Secondary Component ◽  
Spectral Features ◽  
Dark Matter Annihilation ◽  
Positron Fraction ◽  
Positron Flux

Abstract Cosmic-ray positrons have long been considered a powerful probe of dark matter annihilation. In particular, myriad studies of the unexpected rise in the positron fraction have debated its dark matter or pulsar origins. In this paper, we instead examine the potential for extremely precise positron measurements by AMS-02 to probe hard leptophilic dark matter candidates that do not have spectral features similar to the bulk of the observed positron excess. Utilizing a detailed cosmic-ray propagation model that includes a primary positron flux generated by Galactic pulsars in addition to a secondary component constrained by He and proton measurements, we produce a robust fit to the local positron flux and spectrum. We find no evidence for a spectral bump correlated with leptophilic dark matter, and set strong constraints on the dark matter annihilation cross-section that fall below the thermal annihilation cross-section for dark matter masses below 60 GeV and 380 GeV for annihilation into τ+τ- and e+e-, respectively, in our default model.

scholarly journals Spin-one dark matter and gamma ray signals from the galactic center

2020 ◽  
Vol 2020 (8) ◽  
Author(s):  
H. Hernández-Arellano ◽  
M. Napsuciale ◽  
S. Rodríguez
Keyword(s):  
Dark Matter ◽  
Cross Section ◽  
Gamma Ray ◽  
Galactic Center ◽  
Photon Emission ◽  
Scalar Coupling ◽  
Initial State ◽  
Internal Bremsstrahlung ◽  
Resonance Effects ◽  
State Radiation

Abstract In this work we study the possibility that the gamma ray excess (GRE) at the Milky Way galactic center come from the annihilation of dark matter with a (1, 0) ⊕ (0, 1) space-time structure (spin-one dark matter, SODM). We calculate the production of prompt photons from initial state radiation, internal bremsstrahlung, final state radiation including the emission from the decay products of the μ, τ or hadronization of quarks. Next we study the delayed photon emission from the inverse Compton scattering (ICS) of electrons (produced directly or in the prompt decay of μ, τ leptons or in the hadronization of quarks produced in the annihilation of SODM) with the cosmic microwave background or starlight. All these mechanisms yield significant contributions only for Higgs resonant exchange, i.e. for M ≈ MH /2, and the results depend on the Higgs scalar coupling to SODM, gs. The dominant mechanism at the GRE bump is the prompt photon production in the hadronization of b quarks produced in $$ \overline{D}D\to \overline{b}b $$ D ¯ D → b ¯ b , whereas the delayed photon emission from the ICS of electrons coming from the hadronization of b quarks produced in the same reaction dominates at low energies (ω < 0.3 GeV ) and prompt photons from c and τ , as well as from internal bremsstrahlung, yield competitive contributions at the end point of the spectrum (ω ≥ 30 GeV ). Taking into account all these contributions, our results for photons produced in the annihilation of SODM are in good agreement with the GRE data for gs ∈ [0.98, 1.01] × 10−3 and M ∈ [62.470, 62.505] GeV . We study the consistency of the corresponding results for the dark matter relic density, the spin-independent dark matter-nucleon cross-section σp and the cross section for the annihilation of dark matter into $$ \overline{b}b $$ b ¯ b , τ+τ−, μ+μ− and γγ, taking into account the Higgs resonance effects, finding consistent results in all cases.

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