2,984 research outputs found
TASI 2009 Lectures: Searching for Unexpected Physics at the LHC
These TASI lectures consider low mass hidden sectors from Hidden Valleys,
Quirks and Unparticles. We show how each corresponds to a different limit of
the same class of models: hidden sectors with non-abelian gauge groups with
mass gaps well below a TeV that communicate to the Standard Model through weak
scale suppressed higher dimension operators. We provide concrete examples of
such models and discuss LHC signatures. Lastly we turn to discussing the
application of Hidden Valleys to dark matter sectors.Comment: 35 pages, 21 figure
Multi-Component Dark Matter
We explore multi-component dark matter models where the dark sector consists
of multiple stable states with different mass scales, and dark forces coupling
these states further enrich the dynamics. The multi-component nature of the
dark matter naturally arises in supersymmetric models, where both R parity and
an additional symmetry, such as a , is preserved. We focus on a particular
model where the heavier component of dark matter carries lepton number and
annihilates mostly to leptons. The heavier component, which is essentially a
sterile neutrino, naturally explains the PAMELA, ATIC and synchrotron signals,
without an excess in antiprotons which typically mars other models of weak
scale dark matter. The lighter component, which may have a mass from a GeV to a
TeV, may explain the DAMA signal, and may be visible in low threshold runs of
CDMS and XENON, which search for light dark matter.Comment: 4 pages, no figures. v2: paper shortened to letter length; modified
dark matter spectru
Unconditional Pointer States from Conditional Master Equations
When part of the environment responsible for decoherence is used to extract
information about the decohering system, the preferred {\it pointer states}
remain unchanged. This conclusion -- reached for a specific class of models --
is investigated in a general setting of conditional master equations using
suitable generalizations of predictability sieve. We also find indications that
the einselected states are easiest to infer from the measurements carried out
on the environment.Comment: 4 pages, 3 .eps figures; final version to appear in Phys.Rev.Let
Quantum Darwinism requires an extra-theoretical assumption of encoding redundancy
Observers restricted to the observation of pointer states of apparatus cannot
conclusively demonstrate that the pointer of an apparatus A registers the state
of a system of interest S without perturbing S. Observers cannot, therefore,
conclusively demonstrate that the states of a system S are redundantly encoded
by pointer states of multiple independent apparatus without destroying the
redundancy of encoding. The redundancy of encoding required by quantum
Darwinism must, therefore, be assumed from outside the quantum-mechanical
formalism and without the possibility of experimental demonstration.Comment: 5 pages, 1 figure. Comments on foundational assumptions of W. Zurek
(2009) Nat Phys 5 181 (arXiv 0903.5082). v2 significant revision to improve
clarit
A Natural Supersymmetric Model with MeV Dark Matter
It has previously been proposed that annihilating dark matter particles with
MeV-scale masses could be responsible for the flux of 511 keV photons observed
from the region of the Galactic Bulge. The conventional wisdom, however, is
that it is very challenging to construct a viable particle physics model
containing MeV dark matter. In this letter, we challenge this conclusion by
describing a simple and natural supersymmetric model in which the lightest
supersymmetric particle naturally has a MeV-scale mass and the other
phenomenological properties required to generate the 511 keV emission. In
particular, the small ( ) effective couplings between dark
matter and the Standard Model fermions required in this scenario naturally lead
to radiative corrections that generate MeV-scale masses for both the dark
matter candidate and the mediator particle.Comment: 4 pages, 1 figure. v2: Small modification to discussion of spectru
Spacetime Fluctuations in AdS/CFT
We compute fluctuations in the modular energy of the vacuum associated with a
Rindler-wedge in AdS spacetime in the context of AdS/CFT. We discuss the
possible effect of these energy fluctuations on the spacetime geometry, and on
the traversal time of a light beam propagating from the boundary to the bulk
and back.Comment: 25 pages, 1 figur
Indirect Detection Signatures for the Origin of Asymmetric Dark Matter
We study the decay signatures of Asymmetric Dark Matter (ADM) via higher
dimension operators which are responsible for generating the primordial dark
matter (DM) asymmetry. Since the signatures are sensitive both to the nature of
the higher dimension operator generating the DM asymmetry and to the sign of
the baryon or lepton number that the DM carries, indirect detection may provide
a window into the nature of the mechanism which generates the DM asymmetry. We
consider in particular dimension-6 fermionic operators of the form , where (or operators related through a Hermitian conjugate) with
the scale around or just below the GUT scale. We derive constraints on ADM
particles both in the natural mass range (around a few GeV), as well as in the
range between 100 GeV to 10 TeV. For light ADM, we focus on constraints from
both the low energy gamma ray data and proton/anti-proton fluxes. For heavy
ADM, we consider -rays and proton/anti-proton fluxes, and we fit
data from AMS-02 and H.E.S.S. (neglecting the Fermi charged particle
fluxes which disagree with AMS-02 below 100 GeV). We show that, although the
best fit regions from electron/positron measurement are still in tension with
other channels on account of the H.E.S.S. measurement at high energies,
compared to an ordinary symmetric dark matter scenario, the decay of DM with a
primordial asymmetry reduces the tension. Better measurement of the flux at
high energy will be necessary to draw a definite conclusion about the viability
of decaying DM as source for the signals.Comment: Constraint from H.E.S.S. for heavy ADM scenario is included.
Constraint from anti-proton flux for light ADM scenario is included. Matched
to the version of publicatio
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