Reig, M., Restrepo, D., Valle, J. W. F., & Zapata, O. (2019). Bound-state dark matter with Majorana neutrinos. Phys. Lett. B, 790, 303–307.
Abstract: We propose a simple scenario in which dark matter (DM) emerges as a stable neutral hadronic thermal relic, its stability following from an exact U(1)(D) symmetry. Neutrinos pick up radiatively induced Majorana masses from the exchange of colored DM constituents. There is a common origin for both dark matter and neutrino mass, with a lower bound for neutrinoless double beta decay. Direct DM searches at nuclear recoil experiments will test the proposal, which may also lead to other phenomenological signals at future hadron collider and lepton flavor violation experiments.
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Garcia-Cely, C., Landini, G., & Zapata, O. (2025). Dark matter in QCD-like theories with a theta vacuum: Cosmological and astrophysical implications. Phys. Rev. D, 111(6), 063044–13pp.
Abstract: Quantum chromodynamics (QCD)-like theories in which the dark matter (DM) of the Universe is hypothesized to be a thermal relic in the form of a dark pion has been extensively investigated, with most studies neglecting the CP-violating 0-angle associated with the topological vacuum. We point out that a nonvanishing 0 could potentially trigger resonant number-changing processes giving rise to the observed relic density in agreement with perturbative unitarity as well as observations of clusters of galaxies. This constitutes a novel production mechanism of MeV DM and an alternative to those relying on the Wess-Zumino-Witten term. Moreover, for specific meson mass spectra, similar resonant scatterings serve as a realization of velocity-dependent self-interacting DM without a light mediator. Explicit benchmark models are presented together with a discussion of possible signals, including gravitational waves from the chiral phase transition associated with the dark pions.
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Reig, M., Restrepo, D., Valle, J. W. F., & Zapata, O. (2018). Bound-state dark matter and Dirac neutrino masses. Phys. Rev. D, 97(11), 115032–5pp.
Abstract: We propose a simple theory for the idea that cosmological dark matter (DM) may be present today mainly in the form of stable neutral hadronic thermal relics. In our model, neutrino masses arise radiatively from the exchange of colored DM constituents, giving a common origin for both dark matter and neutrino mass. The exact conservation of B – L symmetry ensures dark matter stability and the Dirac nature of neutrinos. The theory can be falsified by dark matter nuclear recoil direct detection experiments, leading also to possible signals at a next generation hadron collider.
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Restrepo, D., Taoso, M., Valle, J. W. F., & Zapata, O. (2012). Gravitino dark matter and neutrino masses with bilinear R-parity violation. Phys. Rev. D, 85(2), 023523–7pp.
Abstract: Bilinear R-parity violation provides an attractive origin for neutrino masses and mixings. In such schemes the gravitino is a viable decaying dark matter particle whose R-parity violating decays lead to monochromatic photons with rates accessible to astrophysical observations. We determine the parameter region allowed by gamma-ray line searches, dark matter relic abundance, and neutrino oscillation data, obtaining a limit on the gravitino mass m((G) over tilde) less than or similar to 1-10 GeV corresponding to a relatively low reheat temperature T-R less than or similar to few x 10(7)-10(8) GeV. Neutrino mass and mixing parameters may be reconstructed at accelerator experiments like the Large Hadron Collider.
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Garcia-Cely, C., Landini, G., Marsili, L., & Zapata, O. (2026). Pion dark matter in a θ vacuum: a thermal relic with sharp velocity-dependent self-interactions. J. High Energy Phys., 02(2), 105–32pp.
Abstract: As recently proposed, a non-vanishing topological angle may play a central role in QCD-like theories of dark matter (DM). In this work, we introduce a dark photon portal to the Standard Model in order to establish thermal equilibrium in the early Universe, and discuss the ensuing phenomenological constraints, including the stability of DM. accounts for the observed DM relic abundance and yields velocity-dependent DM self-interactions in astrophysical halos. Due to the sharp velocity dependence arising from a Breit-Wigner resonance, dedicated studies are required to assess the gravothermal evolution in detail, especially in the core-collapse regime. This is particularly timely in light of self-interacting DM interpretations of strong-lensing systems such as SDSS J0946+1006, which can be naturally explained within our framework.
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