Dirac dark matter with a charged mediator: a comprehensive one-loop analysis of the direct detection phenomenology

Alejandro Ibarra,Sebastian Wild

doi:10.1088/1475-7516/2015/05/047

Alejandro Ibarra, Sebastian Wild

Open Access

https://doi.org/10.1088/1475-7516/2015/05/047

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Abstract

We analyze the direct detection signals of a toy model consisting of a Dirac dark matter particle which couples to one Standard Model fermion via a scalar mediator. For all scenarios, the dark matter particle scatters off nucleons via one loop-induced electromagnetic and electroweak moments, as well as via the one-loop exchange of a Higgs boson. Besides, and depending on the details of the model, the scattering can also be mediated at tree level via the exchange of the scalar mediator or at one loop via gluon-gluon interactions. We show that, for thermally produced dark matter particles, the current limits from the LUX experiment on these scenarios are remarkably strong, even for dark matter coupling only to leptons. We also discuss future prospects for XENON1T and DARWIN and we argue that multi-ton xenon detectors will be able to probe practically the whole parameter space of the model consistent with thermal production and perturbativity. We also discuss briefly the implications of our results for the dark matter interpretation of the Galactic GeV excess.

Highlights

Thermal parameter spaceThree parameters: DM mass mχ, mass splitting mη /mχ, Yukawa coupling y The requirement of Ωχh2 0.12 xes y ≡ ythermal(mχ, mη/mχ)
Consider a Dirac dark matter particle χ tree-level If χ can scatter of nucleons N at via the exchange of a Z ...:
The IceCube/Super-K limits can be very strong for leptophilic annihilations, e.g. DM DM → τ +τ − or DM DM → νν The magnetic dipole moment of χ leads to a dipole-dipole interaction with protons

Summary

Thermal parameter space

Three parameters: DM mass mχ, mass splitting mη /mχ, Yukawa coupling y The requirement of Ωχh2 0.12 xes y ≡ ythermal(mχ, mη/mχ). → main annihilation channel for the freeze-out: χχ → f f → For mη /mχ 1.2, coannihilations are important, e.g. ηη† → γγ DM mass mχ, mass splitting mη /mχ, Yukawa coupling y. The requirement of Ωχh2 0.12 xes y ≡ ythermal(mχ, mη/mχ) → main annihilation channel for the freeze-out: χχ → f f. ), the thermal parameter space is only two-dimensional, spanned by mχ and mη /mχ For every coupling scenario (eR, uR, . . . ), the thermal parameter space is only two-dimensional, spanned by mχ and mη /mχ

Intermediate outline

LUX already excludes almost the

Coupling to τR

Excellent prospects for future direct detection experiments

Conclusions