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}Dto overline{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 , τ+τ−, μ+μ− and γγ, taking into account the Higgs resonance effects, finding consistent results in all cases.
Highlights
Taking into account all these contributions, our results for photons produced in the annihilation of spin-one dark matter (SODM) are in good agreement with the gamma ray excess (GRE) data for gs ∈ [0.98, 1.01]×10−3 and M ∈ [62.470, 62.505] GeV
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
The dominant mechanism at the GRE bump is the prompt photon production in the hadronization of b quarks produced in D D → ̄bb, whereas the delayed photon emission from the inverse Compton scattering (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 )
Summary
During the past few years, it has been claimed by several groups that an excess over the expected gamma ray flux from known sources in the Milky Way galactic center exists in the FermiLAT data around 3 GeV [15,16,17,18,19,20,21,22,23,24,25]. It is conventionally assumed that this non-radiative cross section contains all the information on the annihilation of dark matter entering the radiative process, in such a way that the spectrum has the information of the photon production from standard model i-states which can be calculated and, beyond technical details, it is well known. In this construction, model independent fits to data can be done with σvr i and M as free parameters. In [37], it was shown that the muon channel yield sizable contributions to the GRE and when added to the prompt photon production in this channel allows for higher values of the dark matter mass (M ≈ 61 GeV ), with the required cross section still being of the order of the thermal cross section
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