Abstract
Dark matter (DM) constitutes 85% of the matter in the Universe. However, its specific particle property is still unclear. The fundamentals of DM particles subject to gravitational interaction, and that the lepton excess in cosmic rays may originate from DM particles, inspired us to investigate DM particle properties beyond the standard model. We assume that a leptophilic SU(2) doublet exists in nature as the mediator connecting DM with visible leptons. Since general relativity is not renormalizable at the quantum level, it should be regarded as an effective field theory’s leading order term. One species of the next-to-leading-order term should be operators linear to the Ricci scalar and containing scalar fields, such as the Higgs field, scalar DM, or the newly introduced SU(2) scalar doublet. These operators can cause DM annihilation through gravity portals. We analyzed constraints from the cosmic antiproton flux, DM relic abundance, cosmic positron flux, cosmic microwave background, and direct detection experiments. The result shows that there is a vast parameter space that is compatible with current experiments. DM with a mass of electroweak scale is only allowed to annihilate into leptons. We further show that the purely gravitational DM better explains the DArk Matter Particle Explorer cosmic lepton excess. Our work provides a promising mechanism for DM particles to connect with standard model particles.
Highlights
Our work provides a promising mechanism for Dark matter (DM) particles to connect with standard model particles
A dynamical DM decay model was proposed to explain the cosmic-ray positron fraction observed by AMS-02, which satisfies the constraints from FERMI and Planck [16]
Based on the fact that most evidence of DM comes from gravitational interaction, this work assumes that DM is only subject to gravitational interaction
Summary
Despite the great success of DM research in the Λ-cold-DM (ΛCDM) model, general relativity is not the correct theory at the quantum level because it is not renormalizable. Because physicists found the Higgs boson on the Large Hadron Collider, an additional dimension-four operator, −ξh(H†H)R, should be present as the next to leading-order term in the effective theory, where H represents the Higgs doublet, and ξh is the coupling constant [32]. It is the lowest dimension operator and the only dimension-four operator among all the operators that Standard Model fields couple to gravity nonminimally. This work found that after electroweak symmetry breaking, two dimension-four operators, −ξη(H†Φ + Φ†H)R and −ξφφ2R, act together, which can lead to efficient DM annihilation
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