3,086 research outputs found
Gravitational Lensing and the Variability of G
The four observables associated with gravitational lensing of distant quasars
by intervening galaxies: image splittings, relative amplifications, time
delays, and optical depths, provide separate measures of the strength of the
gravitational constant at cosmological distances. These allow one, in
principle, to factor out unknown lensing parameters to directly to probe the
variation of over cosmological time. We estimate constraints on
which may be derivable by this method both now and in the future. The limits
one may obtain can compete or exceed other direct limits on today,
but unfortunately extracting this information, is not independent of the effort
to fix other cosmological parameters such as and from lensing
observations.Comment: 13 pages plus figures (not included
Impact of a XENONnT Signal on LHC Dijet Searches
It is well-known that dark matter (DM) direct detection experiments and the
LHC are complementary, since they probe physical processes occurring at
different energy scales. And yet, there are aspects of this complementarity
which are still not fully understood, or exploited. For example, what is the
impact that the discovery of DM at XENONnT would have on present and future
searches for DM in LHC final states involving a pair of hadronic jets? In this
work we investigate the impact of a XENONnT signal on the interpretation of
current dijet searches at the LHC, and on the prospects for dijet signal
discovery at the High-Luminosity (HL) LHC in the framework of simplified
models. Specifically, we focus on a general class of simplified models where DM
can have spin 0, 1/2 or 1, and interacts with quarks through the exchange of a
scalar, pseudo-scalar, vector, or pseudo-vector mediator. We find that
exclusion limits on the mediator's mass and its coupling to quarks from dijet
searches at the LHC are significantly affected by a signal at XENONnT, and that
signal events at XENONnT would drastically narrow the region
in the parameter space of simplified models where a dijet signal can be
discovered at C.L. at the HL-LHC.Comment: 23 pages, 3 figures, 3 tables, version accepted by JHE
Flexible metamaterials at visible wavelengths
We report on the fabrication and characterization of plasmonic structures on flexible substrates (Metaflex) and demonstrate the optical properties of a single layer of Metaflex. The layer exhibits a plasmonic resonance in the visible region around 620 nm. We show experimental and numerical results for both nano-antennas and fishnet geometries. We anticipate the use of Metaflex as a building block for flexible metamaterials in the visible range.Publisher PDFPeer reviewe
Minimal Asymmetric Dark Matter
In the early Universe, any particle carrying a conserved quantum number and
in chemical equilibrium with the thermal bath will unavoidably inherit a
particle-antiparticle asymmetry. A new particle of this type, if stable, would
represent a candidate for asymmetric dark matter (DM) with an asymmetry
directly related to the baryon asymmetry. We study this possibility for a
minimal DM sector constituted by just one (generic) multiplet
carrying hypercharge, assuming that at temperatures above the electroweak phase
transition an effective operator enforces chemical equilibrium between
and the Higgs boson. We argue that limits from DM direct detection searches
severely constrain this scenario, leaving as the only possibilities scalar or
fermion multiplets with hypercharge , preferentially quintuplets or
larger representations, and with a mass in the few TeV range.Comment: 9 pages, 2 figures, included t-channel scattering, added details on
charged-neutral mass splitting and indirect detection, accepted in PL
Higher Dimensional Effective Operators for Direct Dark Matter Detection
We discuss higher dimensional effective operators describing interactions
between fermionic dark matter and Standard Model particles. They are typically
suppressed compared to the leading order effective operators, which can explain
why no conclusive direct dark matter detection has been made so far. The
ultraviolet completions of the effective operators, which we systematically
study, require new particles. These particles can potentially have masses at
the TeV scale and can therefore be phenomenologically interesting for LHC
physics. We demonstrate that the lowest order options require Higgs-portal
interactions generated by dimension six operators. We list all possible
tree-level completions with extra fermions and scalars, and we discuss the LHC
phenomenology of a specific example with extra heavy fermion doublets.Comment: 27 pages, 11 figures, 3 table
Soft Gamma Rays from Heavy WIMPs
We propose an explanation of the galactic center gamma ray excess by
supersymmetric WIMPs as heavy as 500 GeV. The lightest neutralino annihilates
into vector-like leptons or quarks which cascade decay through intermediate
Higgs bosons. Due to the long decay chains, the gamma ray spectrum is much
softer than naively expected and peaks at GeV energies. The model predicts
correlated diboson and dijet signatures to be tested at the LHC.Comment: 8 pages, 8 figures; v2: focus on gamma ray excess, matches published
versio
Determining Dark Matter properties with a XENONnT/LZ signal and LHC-Run3 mono-jet searches
We develop a method to forecast the outcome of the LHC Run 3 based on the
hypothetical detection of signal events at XENONnT. Our
method relies on a systematic classification of renormalisable single-mediator
models for dark matter-quark interactions, and is valid for dark matter
candidates of spin less than or equal to one. Applying our method to simulated
data, we find that at the end of the LHC Run 3 only two mutually exclusive
scenarios would be compatible with the detection of signal
events at XENONnT. In a first scenario, the energy distribution of the signal
events is featureless, as for canonical spin-independent interactions. In this
case, if a mono-jet signal is detected at the LHC, dark matter must have spin
1/2 and interact with nucleons through a unique velocity-dependent operator. If
a mono-jet signal is not detected, dark matter interacts with nucleons through
canonical spin-independent interactions. In a second scenario, the spectral
distribution of the signal events exhibits a bump at non zero recoil energies.
In this second case, a mono-jet signal can be detected at the LHC Run 3, dark
matter must have spin 1/2 and interact with nucleons through a unique
momentum-dependent operator. We therefore conclude that the observation of
signal events at XENONnT combined with the detection, or the
lack of detection, of a mono-jet signal at the LHC Run 3 would significantly
narrow the range of possible dark matter-nucleon interactions. As we argued
above, it can also provide key information on the dark matter particle spin.Comment: 17 pages, 8 figures, updated operator coefficients and figures,
version accepted by PR
A constrained supersymmetric left-right model
We present a supersymmetric left-right model which predicts gauge coupling
unification close to the string scale and extra vector bosons at the TeV scale.
The subtleties in constructing a model which is in agreement with the measured
quark masses and mixing for such a low left-right breaking scale are discussed.
It is shown that in the constrained version of this model radiative breaking of
the gauge symmetries is possible and a SM-like Higgs is obtained. Additional
CP-even scalars of a similar mass or even much lighter are possible. The
expected mass hierarchies for the supersymmetric states differ clearly from
those of the constrained MSSM. In particular, the lightest down-type squark,
which is a mixture of the sbottom and extra vector-like states, is always
lighter than the stop. We also comment on the model's capability to explain
current anomalies observed at the LHC.Comment: 21 pages, 5 figures; v2: references added, matches published versio
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