434
M. Dutra
density increases with DM mass, we need smaller overall couplings in order to not
overproduce the FIMPs and therefore Λ needs to be raised for a given relic density
value. Also, due to the exponential Boltzmann suppression, the thermal bath cannot
produce dark matter much before the time of maximal temperature and Λ is sharply
lowered as to compensate the suppressed rates. In the upper panel, the pole of the
axial modulus is reached inside the radiation era. Since it enhances the relic densities
of vector and fermionic DM candidates, we need higher values of Λ. Notice that the
curves for the fermionic DM depend strongly on the DM mass, due to the chirality
flip. In the lower panel, the exchange of a heavier real modulus suppresses more the
relic densities, so that we can have lower values of Λ, but still at intermediate scales.
4 Concluding Remarks
In this conference, I have discussed the case in which heavy moduli fields exchange
between visible and dark matter are the underlying physics of the feeble couplings
necessary for the freeze-in to happen. Such fields appear in many structural
extensions of the SM, and our results are expected to be embedded in more realistic
realizations. We have seen that if the temperature dependencies of the production
rates of FIMPs are strong enough, which can be achieved in effective models with
derivative couplings, FIMPs would have already been produced at the start of the
radiation era. As an interesting outcome, in a wide range of our parameter space
a good relic density is “naturally” achieved for scalar, fermionic, and vector FIMP
candidates with the moduli masses at intermediate scales, and for reasonable scales
of new physics.
Acknowledgments I want to thank the co-authors of the work presented in this conference,
Debtosh Chowdhury, Emilian Dudas, and Yann Mambrini. I also acknowledge the support from
the Brazilian PhD program “Ciências sem Fronteiras”-CNPQ Process No. 202055/2015-9 during
the development of this work and the current support of the Arthur B. McDonald Canadian
Astroparticle Physics Research Institute.
References
1. D.J.H. Chung, E.W. Kolb, A. Riotto, Production of massive particles during reheating. Phys.
Rev. D 60, 063504 (1999). https://doi.org/10.1103/PhysRevD.60.063504. [hep-ph/9809453]
2. L.J. Hall, K. Jedamzik, J. March-Russell, S.M. West, Freeze-in production of FIMP dark
matter. J. High Energy Phys. 1003, 080 (2010). https://doi.org/10.1007/JHEP03(2010)080.
[arXiv:0911.1120 [hep-ph]]
3. N. Bernal, M. Heikinheimo, T. Tenkanen, K. Tuominen, V. Vaskonen, The dawn of FIMP
dark matter: a review of models and constraints. Int. J. Mod. Phys. A 32(27), 1730023 (2017).
https://doi.org/10.1142/S0217751X1730023X. [arXiv:1706.07442 [hep-ph]]
M. Dutra
density increases with DM mass, we need smaller overall couplings in order to not
overproduce the FIMPs and therefore Λ needs to be raised for a given relic density
value. Also, due to the exponential Boltzmann suppression, the thermal bath cannot
produce dark matter much before the time of maximal temperature and Λ is sharply
lowered as to compensate the suppressed rates. In the upper panel, the pole of the
axial modulus is reached inside the radiation era. Since it enhances the relic densities
of vector and fermionic DM candidates, we need higher values of Λ. Notice that the
curves for the fermionic DM depend strongly on the DM mass, due to the chirality
flip. In the lower panel, the exchange of a heavier real modulus suppresses more the
relic densities, so that we can have lower values of Λ, but still at intermediate scales.
4 Concluding Remarks
In this conference, I have discussed the case in which heavy moduli fields exchange
between visible and dark matter are the underlying physics of the feeble couplings
necessary for the freeze-in to happen. Such fields appear in many structural
extensions of the SM, and our results are expected to be embedded in more realistic
realizations. We have seen that if the temperature dependencies of the production
rates of FIMPs are strong enough, which can be achieved in effective models with
derivative couplings, FIMPs would have already been produced at the start of the
radiation era. As an interesting outcome, in a wide range of our parameter space
a good relic density is “naturally” achieved for scalar, fermionic, and vector FIMP
candidates with the moduli masses at intermediate scales, and for reasonable scales
of new physics.
Acknowledgments I want to thank the co-authors of the work presented in this conference,
Debtosh Chowdhury, Emilian Dudas, and Yann Mambrini. I also acknowledge the support from
the Brazilian PhD program “Ciências sem Fronteiras”-CNPQ Process No. 202055/2015-9 during
the development of this work and the current support of the Arthur B. McDonald Canadian
Astroparticle Physics Research Institute.
References
1. D.J.H. Chung, E.W. Kolb, A. Riotto, Production of massive particles during reheating. Phys.
Rev. D 60, 063504 (1999). https://doi.org/10.1103/PhysRevD.60.063504. [hep-ph/9809453]
2. L.J. Hall, K. Jedamzik, J. March-Russell, S.M. West, Freeze-in production of FIMP dark
matter. J. High Energy Phys. 1003, 080 (2010). https://doi.org/10.1007/JHEP03(2010)080.
[arXiv:0911.1120 [hep-ph]]
3. N. Bernal, M. Heikinheimo, T. Tenkanen, K. Tuominen, V. Vaskonen, The dawn of FIMP
dark matter: a review of models and constraints. Int. J. Mod. Phys. A 32(27), 1730023 (2017).
https://doi.org/10.1142/S0217751X1730023X. [arXiv:1706.07442 [hep-ph]]