390 research outputs found
A map of the non-thermal WIMP
We study the effect of the elastic scattering on the non-thermal WIMP, which
is produced by direct decay of heavy particles at the end of reheating. The
non-thermal WIMP becomes important when the reheating temperature is well below
the freeze-out temperature. Usually, two limiting cases have been considered.
One is that the produced high energetic dark matter particles are quickly
thermalized due to the elastic scattering with background radiations. The
corresponding relic abundance is determined by the thermally averaged
annihilation cross-section at the reheating temperature. The other one is that
the initial abundance is too small for the dark matter to annihilate so that
the final relic is determined by the initial amount itself. We study the
regions between these two limits, and show that the relic density depends not
only on the annihilation rate, but also on the elastic scattering rate.
Especially, the relic abundance of the p-wave annihilating dark matter
crucially relies on the elastic scattering rate because the annihilation
cross-section is sensitive to the dark matter velocity. We categorize the
parameter space into several regions where each region has distinctive
mechanism for determining the relic abundance of the dark matter at the present
Universe. The consequence on the (in)direct detection is also studied.Comment: 9 pages, 5 figures; v2: discussion improved, matches version
published in PL
Clockwork graviton contributions to muon
The clockwork mechanism for gravity introduces a tower of massive graviton
modes, "clockwork gravitons," with a very compressed mass spectrum, whose
interaction strengths are much stronger than that of massless gravitons. In
this work, we compute the lowest order contributions of the clockwork gravitons
to the anomalous magnetic moment, , of muon in the context of extra
dimensional model with a five dimensional Planck mass, . We find that the
total contributions are rather insensitive to the detailed model parameters,
and determined mostly by the value of . In order to account for the
current muon anomaly, should be around , and the
size of the extra dimension has to be quite large, m.
For , the clockwork graviton contributions are too small
to explain the current muon anomaly. We also compare the clockwork
graviton contributions with other extra dimension models such as
Randall-Sundrum models or large extra dimension models. We find that the
leading contributions in the small curvature limit are universal, but the
cutoff-independent subleading contributions vary for different background
geometries and the clockwork geometry gives the smallest subleading
contributions.Comment: 14 pages, 4 figures: v3 minor corrections, to appear in PR
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