50,442 research outputs found
How far are the sources of IceCube neutrinos? Constraints from the diffuse TeV gamma-ray background
The nearly isotropic distribution of the TeV-PeV neutrinos recently detected
by IceCube suggests that they come from sources at distance beyond our Galaxy,
but how far they are is largely unknown due to lack of any associations with
known sources. In this paper, we propose that the cumulative TeV gamma-ray
emission accompanying the production of neutrinos can be used to constrain the
distance of these neutrino sources, since the opacity of TeV gamma rays due to
absorption by the extragalactic background light (EBL) depends on the distance
that these TeV gamma rays have travelled. As the diffuse extragalactic TeV
background measured by \emph{Fermi} is much weaker than the expected cumulative
flux associated with IceCube neutrinos, the majority of IceCube neutrinos, if
their sources are transparent to TeV gamma rays, must come from distances
larger than the horizon of TeV gamma rays. We find that above 80\% of the
IceCube neutrinos should come from sources at redshift . Thus, the
chance for finding nearby sources correlated with IceCube neutrinos would be
small. We also find that, to explain the flux of neutrinos under the TeV
gamma-ray emission constraint, the redshift evolution of neutrino source
density must be at least as fast as the the cosmic star-formation rate.Comment: Accepted by ApJ, some minor changes made, 8 pages, 5 figure
A Tale of Two Portals: Testing Light, Hidden New Physics at Future Colliders
We investigate the prospects for producing new, light, hidden states at a
future collider in a Higgsed dark model, which we call the
Double Dark Portal model. The simultaneous presence of both vector and scalar
portal couplings immediately modifies the Standard Model Higgsstrahlung
channel, , at leading order in each coupling. In addition, each
portal leads to complementary signals which can be probed at direct and
indirect detection dark matter experiments. After accounting for current
constraints from LEP and LHC, we demonstrate that a future Higgs
factory will have unique and leading sensitivity to the two portal couplings by
studying a host of new production, decay, and radiative return processes.
Besides the possibility of exotic Higgs decays, we highlight the importance of
direct dark vector and dark scalar production at machines, whose
invisible decays can be tagged from the recoil mass method.Comment: 47 pages, 9 figures, 1 table. v2: references added, version matched
to JHE
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