7,399 research outputs found
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
Topological recursion relations from Pixton's formula
For any genus g \leq 26, and for n \leq 3 in all genus, we prove that every
degree-g polynomial in the psi-classes on Mbar_{g,n} can be expressed as a sum
of tautological classes supported on the boundary with no kappa-classes. Such
equations, which we refer to as topological recursion relations, can be used to
deduce universal equations for the Gromov-Witten invariants of any target.Comment: 17 page
Analytical treatment for the development of electromagnetic cascades in intense magnetic fields
In a strong magnetic field, a high-energy photon can be absorbed and then
produce an electron-positron pair. The produced electron/positron will in turn
radiate a high-energy photon via synchrotron radiation, which then initiates a
cascade. We built a one-dimensional Monte-Carlo code to study the development
of the cascade especially after it reaches the saturated status, when almost
all the energy of the primary particles transfers to the photons. The photon
spectrum in this status has a cut-off due to the absorption by magnetic fields,
which is much sharper than the exponential one. Below the cut-off, the spectral
energy distribution (SED) manifest itself as a broken power-law with a spectral
index of and , respectively, below and above the broken energy.
The SED can be fitted by a simple analytical function, which is solely
determined by the product of the cascade scale and the magnetic field
perpendicular to the motion of the particle B_{\perp}, with an accuracy better
than 96\%. The similarity of the spectrum to that from the cascade in an
isotropic black-body photon field is also studied.Comment: 7 pages, 7 figures, minor changes. Version to appear in PR
Diffuse PeV neutrinos from EeV cosmic ray sources: semi-relativistic hypernova remnants in star-forming galaxies
We argue that the excess of sub-PeV/PeV neutrinos recently reported by
IceCube could plausibly originate through pion-production processes in the same
sources responsible for cosmic rays (CRs) with energy above the second knee
around eV. The pion production efficiency for escaping CRs that
produce PeV neutrinos is required to be in such sources. On the
basis of current data, we identify semi-relativistic hypernova remants as
possible sources that satisfy the requirements. By virtue of their fast ejecta,
such objects can accelerate protons to EeV energies, which in turn can interact
with the dense surrounding medium during propagation in their host galaxies to
produce sufficient high-energy neutrinos via proton--proton () collisions.
Their accompanying gamma ray flux can remain below the diffuse isotropic gamma
ray background observed by the {\it Fermi} Large Area Telescope (LAT). In order
to test this scenario and discriminate from alternatives, the density of target
protons/nuclei and the residence time of CRs in the interacting region are
crucial uncertainties that need to be clarified. As long as the neutrinos and
EeV CRs originate from the same source class, detection of PeV
neutrinos may be expected within 5-10 years' operation of IceCube. Together
with further observations in the PeV range, the neutrinos can help in revealing
the currently unknown sources of EeV CRs.Comment: 9 pages, 2 figures; large amount of content added; PRD accepte
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