FreezeIn dark matter with displaced signatures at colliders
Abstract
Dark matter, X, may be generated by new physics at the TeV scale during an early matterdominated (MD) era that ends at temperature T_{R} ≪ TeV. Compared to the conventional radiationdominated (RD) results, yields from both FreezeOut and FreezeIn processes are greatly suppressed by dilution from entropy production, making FreezeOut less plausible while allowing successful FreezeIn with a much larger coupling strength. FreezeIn is typically dominated by the decay of a particle B of the thermal bath, B → X. For a large fraction of the relevant cosmological parameter space, the decay rate required to produce the observed dark matter abundance leads to displaced signals at LHC and future colliders, for any m_{X} in the range keV < m_{X} < m_{B} and for values of m_{B} accessible to these colliders. This result applies whether the early MD era arises after conventional inflation, when T_{R} is the usual reheat temperature, or is a generic MD era with an alternative origin. In the former case, if m_{X} is sufficiently large to be measured from kinematics, the reheat temperature T_{R} can be extracted. Our result is independent of the particular particle physics implementation of B → X, and can occur via any operator of dimension less than 8 (4) for a postinflation (general MD) cosmology. An interesting example is provided by DFS axion theories with TeVscale supersymmetry and axino dark matter of mass GeV to TeV, which is typically overproduced in a conventional RD cosmology. If B is the higgsino, h̃, Higgs, W and Z particles appear at the displaced decays, h̃ → h̃ a, Z ã and h̃^{±} → W^{±} ã. The scale of axion physics, f, is predicted to be in the range (3×10^{8}10^{12}) GeV and, over much of this range, can be extracted from the decay length.
 Publication:

Journal of Cosmology and Astroparticle Physics
 Pub Date:
 December 2015
 DOI:
 10.1088/14757516/2015/12/024
 arXiv:
 arXiv:1506.07532
 Bibcode:
 2015JCAP...12..024C
 Keywords:

 High Energy Physics  Phenomenology
 EPrint:
 26 pages + appendices, 13 figures