Abstract
The clockwork mechanism can explain interactions which are dimensionally very weak without the need for very large mass scales. We present a model in which the clockwork mechanism generates the very small Higgs portal coupling and dark matter particle mass necessary to explain cold dark matter via the freeze-in mechanism. We introduce a TeV-scale scalar clockwork sector which couples to the Standard Model via the Higgs portal. The dark matter particle is the lightest scalar of the clockwork sector. We show that the freeze-in mechanism is dominated by decay of the heavy clockwork scalars to light dark matter scalars and Higgs bosons. In the model considered, we find that freeze-in dark matter is consistent with the clockwork mechanism for global charge $q$ in the range $2 \lesssim q \lesssim 4$ when the number of massive scalars is in the range $10 \leq N \leq 20$. The dark matter scalar mass and portal coupling are independent of $q$ and $N$. For a typical TeV-scale clockwork sector, the dark matter scalar mass is predicted to be of the order of a MeV.
Highlights
The clockwork mechanism [1,2,3] is a way to explain the existence of interactions which are much weaker than those dimensionally expected in a theory with a characteristic mass scale
We find that q 1⁄4 3.62 for a clockwork sector with 10 massive scalars, and q 1⁄4 1.90 for a clockwork sector with 20 massive scalars.6 [The corresponding values of mð1⁄4ma1=ðq − 1ÞÞ are 0.38 and 1.1 TeV, respectively.] These values of q appear to be quite reasonable and show that the clockwork mechanism can naturally generate the necessary light dark matter particle mass and very small coupling required by the freeze-in mechanism
This is quite different from a general freeze-in model, where larger values of the dark matter particle mass can be accommodated by reducing the Higgs portal coupling and so the number density of produced dark matter particles
Summary
The clockwork mechanism [1,2,3] is a way to explain the existence of interactions which are much weaker than those dimensionally expected in a theory with a characteristic mass scale. The generation of very weak interactions without the need for very large mass particles may allow particle physics and cosmology to be explained entirely in terms of a TeV-scale theory. In the case of a scalar clockwork model [2,3], very weak interactions can be achieved by introducing a sector consisting of a chain of N þ 1 fundamental fields πj which transform as the Goldstone bosons of a spontaneously broken global Uð1ÞNþ1 symmetry. In this paper we will present a scalar clockwork version of the Higgs portal freeze-in model which can account for the small portal coupling and dark matter particle mass.
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