451 research outputs found
Dark Matter and Global Symmetries
General considerations in general relativity and quantum mechanics are known
to potentially rule out continuous global symmetries in the context of any
consistent theory of quantum gravity. Assuming the validity of such
considerations, we derive stringent bounds from gamma-ray, X-ray, cosmic-ray,
neutrino, and CMB data on models that invoke global symmetries to stabilize the
dark matter particle. We compute up-to-date, robust model-independent limits on
the dark matter lifetime for a variety of Planck-scale suppressed
dimension-five effective operators. We then specialize our analysis and apply
our bounds to specific models including the Two-Higgs-Doublet, Left-Right,
Singlet Fermionic, Zee-Babu, 3-3-1 and Radiative See-Saw models. {Assuming that
(i) global symmetries are broken at the Planck scale, that (ii) the
non-renormalizable operators mediating dark matter decay have couplings,
that (iii) the dark matter is a singlet field, and that (iv) the dark matter
density distribution is well described by a NFW profile}, we are able to rule
out fermionic, vector, and scalar dark matter candidates across a broad mass
range (keV-TeV), including the WIMP regime.Comment: Matches Published version in Phys.Lett. B760 (2016) 807-81
Static impurities in the kagome lattice: dimer freezing and mutual repulsion
We consider the effects of doping the S = 1/2 kagome lattice with static
impurities. We demonstrate that impurities lower the number of low-lying
singlet states, induce dimer-dimer correlations of considerable spatial extent,
and do not generate free spin degrees of freedom. Most importantly, they
experience a highly unconventional mutual repulsion as a direct consequence of
the strong spin frustration. These properties are illustrated by exact
diagonalization, and reproduced to semi-quantitative accuracy within a dimer
resonating-valence-bond description which affords access to longer length
scales. We calculate the local magnetization induced by doped impurities, and
consider its implications for nuclear magnetic resonance measurements on known
kagome systems.Comment: 9 pages, 12 figure
Augury of Darkness: The Low-Mass Dark Z' Portal
Dirac fermion dark matter models with heavy mediators are
subject to stringent constraints from spin-independent direct searches and from
LHC bounds, cornering them to live near the resonance. Such
constraints can be relaxed, however, by turning off the vector coupling to
Standard Model fermions, thus weakening direct detection bounds, or by
resorting to light masses, below the Z pole, to escape heavy
resonance searches at the LHC. In this work we investigate both cases, as well
as the applicability of our findings to Majorana dark matter. We derive
collider bounds for light gauge bosons using the method,
spin-dependent scattering limits, as well as the spin-independent scattering
rate arising from the evolution of couplings between the energy scale of the
mediator mass and the nuclear energy scale, and indirect detection limits. We
show that such scenarios are still rather constrained by data, and that near
resonance they could accommodate the gamma-ray GeV excess in the Galactic
center.Comment: 25 pages, 6 Figures. Typos correcte
Dark Matter and Dark Forces from a supersymmetric hidden sector
We show that supersymmetric "Dark Force" models with gravity mediation are
viable. To this end, we analyse a simple string-inspired supersymmetric hidden
sector model that interacts with the visible sector via kinetic mixing of a
light Abelian gauge boson with the hypercharge. We include all induced
interactions with the visible sector such as neutralino mass mixing and the
Higgs portal term. We perform a detailed parameter space scan comparing the
produced dark matter relic abundance and direct detection cross sections to
current experiments.Comment: 40 pages, 11 figures comprising 21 plots. 4Mb total size. v2: figures
and references updated; typos removed; some extra explanations added. Matches
version published in PR
Invisible Higgs and Scalar Dark Matter
In this proceeding, we show that when we combined WMAP and the most recent
results of XENON100, the invisible width of the Higgs to scalar dark matter is
negligible(<10%), except in a small region with very light dark matter (< 10
GeV) not yet excluded by XENON100 or around 60 GeV where the ratio can reach
50% to 60%. The new results released by the Higgs searches of ATLAS and CMS set
very strong limits on the elastic scattering cross section.Comment: 4 pages, 2 figures, proceeding TAUP2011 References adde
Origins of the Isospin Violation of Dark Matter Interactions
Light dark matter (DM) with a large DM-nucleon spin-independent cross section
and furthermore proper isospin violation (ISV) may provide
a way to understand the confusing DM direct detection results. Combing with the
stringent astrophysical and collider constraints, we systematically investigate
the origin of ISV first via general operator analyses and further via
specifying three kinds of (single) mediators: A light from chiral
, an approximate spectator Higgs doublet (It can explain the
anomaly simultaneously) and color triplets. In addition, although from an
exotic mixing with generating , we can combine it with
the conventional Higgs to achieve proper ISV. As a concrete example, we propose
the model where the charged light sneutrino is the inelastic
DM, which dominantly annihilates to light dark states such as with sub-GeV
mass. This model can address the recent GoGeNT annual modulation consistent
with other DM direct detection results and free of exclusions.Comment: References added and English greatly improve
The Waning of the WIMP? A Review of Models, Searches, and Constraints
Weakly Interacting Massive Particles (WIMPs) are among the best-motivated
dark matter candidates. In light of no conclusive detection signal yet despite
an extensive search program that combines, often in a complementary way,
direct, indirect, and collider probes, we find it timely to give a broad
overview of the WIMP paradigm. In particular, we review here the theoretical
foundations of the WIMP paradigm, discuss status and prospects of various
detection strategies, and explore future experimental challenges and
opportunities.Comment: 101 pages, 20 figure
Comment on "Quantum Monte Carlo scheme for frustrated Heisenberg antiferromagnets"
Quantum Monte Carlo methods are sophisticated numerical techniques for
simulating interacting quantum systems. In some cases, however, they suffer
from the notorious "sign problem" and become too inefficient to be useful. A
recent publication [J. Wojtkiewicz, Phys. Rev. B 75, 174421 (2007)] claims to
have solved the sign problem for a certain class of frustrated quantum spin
systems through the use of a bipartite valence bond basis. We show in this
Comment that the apparent positivity of the path integral is due to a
misconception about the resolution of the identity operator in this basis, and
that consequently the sign problem remains a severe obstacle for the simulation
of frustrated quantum magnets.Comment: 2 page
(In)visible Z' and dark matter
We study the consequences of an extension of the standard model containing an
invisible extra gauge group under which the SM particles are neutral. We show
that effective operators, generated by loops of heavy chiral fermions charged
under both gauge groups and connecting the new gauge sector to the Standard
Model, can give rise to a viable dark matter candidate. Its annihilations
produce clean visible signals through a gamma-ray line. This would be a smoking
gun signature of such models observable by actual experiments.Comment: 18 pages, 5 figures, version to appear in JHE
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