2,394 research outputs found
The Up-Shot of Inelastic Down-Scattering at CDMS-Si
We study dark matter that inelastically scatters and de-excites in direct
detection experiments, as an interpretation of the CDMS-Si events in light of
the recent LUX data. The constraints from LUX and XENON10 require the
mass-splitting between the DM excited and de-excited states to be keV. At the same time, the CDMS-Si data itself do not allow for a
consistent DM interpretation for mass splittings larger than 200 keV. We find that a low threshold analysis will be needed to rule out this
interpretation of the CDMS-Si events. In a simple model with a kinetically
mixed dark photon, we show that the CDMS-Si rate and the thermal relic
abundance can both be accommodated.Comment: 10 pages, 3 figures; updated to match PRD versio
Corrigan-Ramond Extension of QCD at Nonzero Baryon Density
We investigate the Corrigan-Ramond extension of one massless flavor Quantum
Chromo Dynamics at nonzero quark chemical potential. Since the extension
requires the fermions to transform in the two index antisymmetric
representation of the gauge group, one finds that the number of possible
channels is richer than in the 't Hooft limit. We first discuss the diquark
channels and show that for a number of colors larger than three a new diquark
channel appears. We then study the infinite number of color limit and show that
the Fermi surface is unstable to the formation of the
Deryagin-Grigoriev-Rubakov chiral waves. We discover, differently from the 't
Hooft limit, the possibility of a colored chiral wave breaking the color
symmetry as well as translation invariance.Comment: RevTeX, 14 pages, 2 figure
X-ray Lines from Dark Matter: The Good, The Bad, and The Unlikely
We consider three classes of dark matter (DM) models to account for the
recently observed 3.5 keV line: metastable excited state DM, annihilating DM,
and decaying DM. We study two examples of metastable excited state DM. The
first, millicharged composite DM, has both inelasticity and photon emission
built in, but with a very constrained parameter space. In the second example,
up-scattering and decay come from separate sectors and is thus less
constrained. The decay of the excited state can potentially be detectable at
direct detection experiments. However we find that CMB constraints are at the
border of excluding this as an interpretation of the DAMA signal. The
annihilating DM interpretation of the X-ray line is found to be in tension with
CMB constraints. Lastly, a generalized version of decaying DM can account for
the data with a lifetime exceeding the age of the Universe for masses GeV.Comment: 14 pages, 4 figures; updated to match JCAP published versio
Halo Independent Direct Detection of Momentum-Dependent Dark Matter
We show that the momentum dependence of dark matter interactions with nuclei
can be probed in direct detection experiments without knowledge of the dark
matter velocity distribution. This is one of the few properties of DM
microphysics that can be determined with direct detection alone, given a signal
of dark matter in multiple direct detection experiments with different targets.
Long-range interactions arising from the exchange of a light mediator are one
example of momentum-dependent DM. For data produced from the exchange of a
massless mediator we find for example that the mediator mass can be constrained
to be MeV for DM in the 20-1000 GeV range in a halo-independent
manner.Comment: 15 pages, 4 figures; updated to match published versio
New or Missing Energy? Discriminating Dark Matter from Neutrino Interactions at the LHC
Missing energy signals such as monojets are a possible signature of Dark
Matter (DM) at colliders. However, neutrino interactions beyond the Standard
Model may also produce missing energy signals. In order to conclude that new
"missing particles" are observed the hypothesis of BSM neutrino interactions
must be rejected. In this paper, we first derive new limits on these
Non-Standard neutrino Interactions (NSIs) from LHC monojet data. For heavy NSI
mediators, these limits are much stronger than those coming from traditional
low-energy scattering or oscillation experiments for some flavor
structures. Monojet data alone can be used to infer the mass of the "missing
particle" from the shape of the missing energy distribution. In particular, 13
TeV LHC data will have sensitivity to DM masses greater than 1 TeV. In
addition to the monojet channel, NSI can be probed in multi-lepton searches
which we find to yield stronger limits at heavy mediator masses. The
sensitivity offered by these multi-lepton channels provide a method to reject
or confirm the DM hypothesis in missing energy searches.Comment: 11 pages, 7 figure
On the Direct Detection of Dark Matter Annihilation
We investigate the direct detection phenomenology of a class of dark matter
(DM) models in which DM does not directly interact with nuclei, {but rather}
the products of its annihilation do. When these annihilation products are very
light compared to the DM mass, the scattering in direct detection experiments
is controlled by relativistic kinematics. This results in a distinctive recoil
spectrum, a non-standard and or even absent annual modulation, and the ability
to probe DM masses as low as a 10 MeV. We use current LUX data to show
that experimental sensitivity to thermal relic annihilation cross sections has
already been reached in a class of models. Moreover, the compatibility of dark
matter direct detection experiments can be compared directly in
space without making assumptions about DM astrophysics, mass, or scattering
form factors. Lastly, when DM has direct couplings to nuclei, the limit from
annihilation to relativistic particles in the Sun can be stronger than that of
conventional non-relativistic direct detection by more than three orders of
magnitude for masses in a 2-7 GeV window.Comment: 4 pages, 3 figures, PRL versio
Synthesis and catalytic performance of CeOCl in Deacon reaction
Surface chlorinated CeO2 is an efficient material for HCl oxidation, which raises the question whether an oxychloride phase could be also active in the same reaction. CeOCl was synthesized by solid state reaction of cerium oxide with anhydrous cerium chloride and tested in HCl oxidation using various feed compositions at 703 K. X-ray diffraction of post-reaction samples revealed that CeOCl is unstable, in both oxygen-rich and -lean conditions. Applying oxygen over-stoichiometric feeds led to complete transformation of CeOCl into CeO2. Considerable HCl conversions were obtained only after this transformation, which confirms the essential role of bulk cerium oxide in this catalytic system
Minimal Walking Technicolor: Set Up for Collider Physics
Different theoretical and phenomenological aspects of the Minimal and
Nonminimal Walking Technicolor theories have recently been studied. The goal
here is to make the models ready for collider phenomenology. We do this by
constructing the low energy effective theory containing scalars, pseudoscalars,
vector mesons and other fields predicted by the minimal walking theory. We
construct their self-interactions and interactions with standard model fields.
Using the Weinberg sum rules, opportunely modified to take into account the
walking behavior of the underlying gauge theory, we find interesting relations
for the spin-one spectrum. We derive the electroweak parameters using the newly
constructed effective theory and compare the results with the underlying gauge
theory. Our analysis is sufficiently general such that the resulting model can
be used to represent a generic walking technicolor theory not at odds with
precision data.Comment: 42 pages, 3 figures. RevTex forma
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