96 research outputs found
Sommerfeld Enhancement from Multiple Mediators
We study the Sommerfeld enhancement experienced by a scattering object that
couples to a tower of mediators. This can occur in, e.g., models of secluded
dark matter when the mediator scale is generated naturally by hidden-sector
confinement. Specializing to the case of a confining CFT, we show that
off-resonant values of the enhancement can be increased by ~ 20% for cases of
interest when (i) the (strongly-coupled) CFT admits a weakly-coupled dual
description and (ii) the conformal symmetry holds up to the Planck scale.
Larger enhancements are possible for lower UV scales due to an increase in the
coupling strength of the tower.Comment: 17p, 2 figures; v2 JHEP version (inconsequential typo fixed,
references added
Magnetic Fluffy Dark Matter
We explore extensions of inelastic Dark Matter and Magnetic inelastic Dark
Matter where the WIMP can scatter to a tower of heavier states. We assume a
WIMP mass GeV and a constant splitting between
successive states keV. For the
spin-independent scattering scenario we find that the direct experiments CDMS
and XENON strongly constrain most of the DAMA/LIBRA preferred parameter space,
while for WIMPs that interact with nuclei via their magnetic moment a region of
parameter space corresponding to GeV and keV
is allowed by all the present direct detection constraints.Comment: 16 pages, 6 figures, added comments about magnetic moment form factor
to Sec 3.1.2 and results to Sec 3.2.2, final version to be published in JHE
The Dark Side of the Electroweak Phase Transition
Recent data from cosmic ray experiments may be explained by a new GeV scale
of physics. In addition the fine-tuning of supersymmetric models may be
alleviated by new O(GeV) states into which the Higgs boson could decay. The
presence of these new, light states can affect early universe cosmology. We
explore the consequences of a light (~ GeV) scalar on the electroweak phase
transition. We find that trilinear interactions between the light state and the
Higgs can allow a first order electroweak phase transition and a Higgs mass
consistent with experimental bounds, which may allow electroweak baryogenesis
to explain the cosmological baryon asymmetry. We show, within the context of a
specific supersymmetric model, how the physics responsible for the first order
phase transition may also be responsible for the recent cosmic ray excesses of
PAMELA, FERMI etc. We consider the production of gravity waves from this
transition and the possible detectability at LISA and BBO
Decaying into the Hidden Sector
The existence of light hidden sectors is an exciting possibility that may be
tested in the near future. If DM is allowed to decay into such a hidden sector
through GUT suppressed operators, it can accommodate the recent cosmic ray
observations without over-producing antiprotons or interfering with the
attractive features of the thermal WIMP. Models of this kind are simple to
construct, generic and evade all astrophysical bounds. We provide tools for
constructing such models and present several distinct examples. The light
hidden spectrum and DM couplings can be probed in the near future, by measuring
astrophysical photon and neutrino fluxes. These indirect signatures are
complimentary to the direct production signals, such as lepton jets, predicted
by these models.Comment: 40 pages, 5 figure
Singlet Portal to the Hidden Sector
Ultraviolet physics typically induces a kinetic mixing between gauge singlets
which is marginal and hence non-decoupling in the infrared. In singlet
extensions of the minimal supersymmetric standard model, e.g. the
next-to-minimal supersymmetric standard model, this furnishes a well motivated
and distinctive portal connecting the visible sector to any hidden sector which
contains a singlet chiral superfield. In the presence of singlet kinetic
mixing, the hidden sector automatically acquires a light mass scale in the
range 0.1 - 100 GeV induced by electroweak symmetry breaking. In theories with
R-parity conservation, superparticles produced at the LHC invariably cascade
decay into hidden sector particles. Since the hidden sector singlet couples to
the visible sector via the Higgs sector, these cascades necessarily produce a
Higgs boson in an order 0.01 - 1 fraction of events. Furthermore,
supersymmetric cascades typically produce highly boosted, low-mass hidden
sector singlets decaying visibly, albeit with displacement, into the heaviest
standard model particles which are kinematically accessible. We study
experimental constraints on this broad class of theories, as well as the role
of singlet kinetic mixing in direct detection of hidden sector dark matter. We
also present related theories in which a hidden sector singlet interacts with
the visible sector through kinetic mixing with right-handed neutrinos.Comment: 12 pages, 5 figure
An Electron Fixed Target Experiment to Search for a New Vector Boson A' Decaying to e+e-
We describe an experiment to search for a new vector boson A' with weak
coupling alpha' > 6 x 10^{-8} alpha to electrons (alpha=e^2/4pi) in the mass
range 65 MeV < m_A' < 550 MeV. New vector bosons with such small couplings
arise naturally from a small kinetic mixing of the "dark photon" A' with the
photon -- one of the very few ways in which new forces can couple to the
Standard Model -- and have received considerable attention as an explanation of
various dark matter related anomalies. A' bosons are produced by radiation off
an electron beam, and could appear as narrow resonances with small production
cross-section in the trident e+e- spectrum. We summarize the experimental
approach described in a proposal submitted to Jefferson Laboratory's PAC35,
PR-10-009. This experiment, the A' Experiment (APEX), uses the electron beam of
the Continuous Electron Beam Accelerator Facility at Jefferson Laboratory
(CEBAF) at energies of ~1-4 GeV incident on 0.5-10% radiation length Tungsten
wire mesh targets, and measures the resulting e+e- pairs to search for the A'
using the High Resolution Spectrometer and the septum magnet in Hall A. With a
~1 month run, APEX will achieve very good sensitivity because the statistics of
e+e- pairs will be ~10,000 times larger in the explored mass range than any
previous search for the A' boson. These statistics and the excellent mass
resolution of the spectrometers allow sensitivity to alpha'/alpha one to three
orders of magnitude below current limits, in a region of parameter space of
great theoretical and phenomenological interest. Similar experiments could also
be performed at other facilities, such as the Mainz Microtron.Comment: 19 pages, 12 figures, 2 table
Dark Force Detection in Low Energy e-p Collisions
We study the prospects for detecting a light boson X with mass m_X < 100 MeV
at a low energy electron-proton collider. We focus on the case where X
dominantly decays to e+ e- as motivated by recent "dark force" models. In order
to evade direct and indirect constraints, X must have small couplings to the
standard model (alpha_X 10 MeV).
By comparing the signal and background cross sections for the e- p e+ e- final
state, we conclude that dark force detection requires an integrated luminosity
of around 1 inverse attobarn, achievable with a forthcoming JLab proposal.Comment: 38 pages, 19 figures; v2, references adde
Secluded Dark Matter Coupled to a Hidden CFT
Models of secluded dark matter offer a variant on the standard WIMP picture
and can modify our expectations for hidden sector phenomenology and detection.
In this work we extend a minimal model of secluded dark matter, comprised of a
U(1)'-charged dark matter candidate, to include a confining hidden-sector CFT.
This provides a technically natural explanation for the hierarchically small
mediator-scale, with hidden-sector confinement generating m_{gamma'}>0.
Furthermore, the thermal history of the universe can differ markedly from the
WIMP picture due to (i) new annihilation channels, (ii) a (potentially) large
number of hidden-sector degrees of freedom, and (iii) a hidden-sector phase
transition at temperatures T << M_{dm} after freeze out. The mediator allows
both the dark matter and the Standard Model to communicate with the CFT, thus
modifying the low-energy phenomenology and cosmic-ray signals from the secluded
sector.Comment: ~50p, 8 figs; v2 JHEP versio
Asymmetric Dark Matter from Leptogenesis
We present a new realization of asymmetric dark matter in which the dark
matter and lepton asymmetries are generated simultaneously through two-sector
leptogenesis. The right-handed neutrinos couple both to the Standard Model and
to a hidden sector where the dark matter resides. This framework explains the
lepton asymmetry, dark matter abundance and neutrino masses all at once. In
contrast to previous realizations of asymmetric dark matter, the model allows
for a wide range of dark matter masses, from keV to 10 TeV. In particular, very
light dark matter can be accommodated without violating experimental
constraints. We discuss several variants of our model that highlight
interesting phenomenological possibilities. In one, late decays repopulate the
symmetric dark matter component, providing a new mechanism for generating a
large annihilation rate at the present epoch and allowing for mixed warm/cold
dark matter. In a second scenario, dark matter mixes with the active neutrinos,
thus presenting a distinct method to populate sterile neutrino dark matter
through leptogenesis. At late times, oscillations and dark matter decays lead
to interesting indirect detection signals.Comment: 32 pages + appendix, references added, minor change
Interplay between Fermi gamma-ray lines and collider searches
We explore the interplay between lines in the gamma-ray spectrum and LHC searches involving missing energy and photons. As an example, we consider a singlet Dirac
fermion dark matter with the mediator for Fermi gamma-ray line at 130 GeV. A new chiral or local U(1) symmetry makes weak-scale dark matter natural and provides the axion or
Z 0 gauge boson as the mediator connecting between dark matter and electroweak gauge bosons. In these models, the mediator particle can be produced in association with a
monophoton at colliders and it produces large missing energy through the decays into a DM pair or ZZ; Z with at least one Z decaying into a neutrino pair. We adopt the monophoton searches with large missing energy at the LHC and impose the bounds on the coupling and mass of the mediator field in the models. We show that the parameter space of the Z 0 mediation model is already strongly constrained by the LHC 8TeV data, whereas a certain region of the parameter space away from the resonance in axion-like mediator models are bounded. We foresee the monophoton bounds on the Z 0 and axion mediation models at the LHC 14 TeV
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