Urbano Franca, Roberto A. Lineros, Joaquim Palacio, Sergio Pastor
The nature of dark matter is one of the most thrilling riddles for both cosmology and particle physics nowadays. While in the typical models the dark sector is composed only by weakly interacting massive particles, an arguably more natural scenario would include a whole set of gauge interactions which are invisible for the standard model but that are in contact with the dark matter. We present a method to constrain the number of massless gauge bosons and other relativistic particles that might be present in the dark sector using current and future cosmic microwave background data, and provide upper bounds on its size. We use the fact that the dark matter abundance depends on the strength of the interactions with both sectors, which allows one to relate the decoupling temperature of the dark matter with temperature of this cosmic dark gauge bosons background. This relation can then be used to calculate how sizable is the impact of the relativistic dark sector in the number of degrees of freedom of the early Universe, providing an interesting and testable connection between cosmological data and direct/indirect detection experiments. While current data from WMAP satellite, ACT, and SPT constrains the number of relativistic dark gauge bosons to be N < 13 for the simplest scenarios, forthcoming data from Planck satellite will improve this number by approximately a factor 3, reducing significantly the parameter space of allowed models.
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http://arxiv.org/abs/1303.1776
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