40 research outputs found
How to save the WIMP: global analysis of a dark matter model with two s-channel mediators
A reliable comparison of different dark matter (DM) searches requires models
that satisfy certain consistency requirements like gauge invariance and
perturbative unitarity. As a well-motivated example, we study two-mediator DM
(2MDM). The model is based on a spontaneously broken gauge symmetry and
contains a Majorana DM particle as well as two -channel mediators, one
vector (the ) and one scalar (the dark Higgs). We perform a global scan
over the parameters of the model assuming that the DM relic density is obtained
by thermal freeze-out in the early Universe and imposing a large set of
constraints: direct and indirect DM searches, monojet, dijet and dilepton
searches at colliders, Higgs observables, electroweak precision tests and
perturbative unitarity. We conclude that thermal DM is only allowed either
close to an -channel resonance or if at least one mediator is lighter than
the DM particle. In these cases a thermal DM abundance can be obtained although
DM couplings to the Standard Model are tiny. Interestingly, we find that
vector-mediated DM-nucleon scattering leads to relevant constraints despite the
velocity-suppressed cross section, and that indirect detection can be important
if DM annihilations into both mediators are kinematically allowed.Comment: 30 pages, 9 figures + appendice
Numerical coupling of aerosol emissions, dry removal, and turbulent mixing in the E3SM Atmosphere Model version 1 (EAMv1), part I: dust budget analyses and the impacts of a revised coupling scheme
An earlier study evaluating the dust life cycle in EAMv1 has revealed that
the simulated global mean dust lifetime is substantially shorter when higher
vertical resolution is used, primarily due to significant strengthening of dust
dry removal in source regions. This paper demonstrates that the sequential
splitting of aerosol emissions, dry removal, and turbulent mixing in the
model's time integration loop, especially the calculation of dry removal after
surface emissions and before turbulent mixing, is the primary reason for the
vertical resolution sensitivity reported in that earlier study. Based on this
reasoning, we propose a simple revision to the numerical process coupling
scheme, which moves the application of the surface emissions to after dry
removal and before turbulent mixing. The revised scheme allows newly emitted
particles to be transported aloft by turbulence before being removed from the
atmosphere, and hence better resembles the dust life cycle in the real world.
Sensitivity experiments are conducted and analyzed to evaluate the impact of
the revised coupling on the simulated aerosol climatology in EAMv1
Coherent driving of direct and indirect excitons in a quantum dot molecule
Quantum dot molecules (QDMs) are one of the few quantum light sources that
promise deterministic generation of one- and two-dimensional photonic graph
states. The proposed protocols rely on coherent excitation of the
tunnel-coupled and spatially indirect exciton states. Here, we demonstrate
power-dependent Rabi oscillations of direct excitons, spatially indirect
excitons, and excitons with a hybridized electron wave function. An
off-resonant detection technique based on phonon-mediated state transfer allows
for spectrally filtered detection under resonant excitation. Applying a gate
voltage to the QDM-device enables a continuous transition between direct and
indirect excitons and, thereby, control of the overlap of the electron and hole
wave function. This does not only vary the Rabi frequency of the investigated
transition by a factor of , but also allows to optimize graph state
generation in terms of optical pulse power and reduction of radiative
lifetimes.Comment: 6 pages, 3 figure
Self-consistent field theory of polarized BEC: dispersion of collective excitation
We suggest the construction of a set of the quantum hydrodynamics equations
for the Bose-Einstein condensate (BEC), where atoms have the electric dipole
moment. The contribution of the dipole-dipole interactions (DDI) to the Euler
equation is obtained. Quantum equations for the evolution of medium
polarization are derived. Developing mathematical method allows to study effect
of interactions on the evolution of polarization. The developing method can be
applied to various physical systems in which dynamics is affected by the DDI.
Derivation of Gross-Pitaevskii equation for polarized particles from the
quantum hydrodynamics is described. We showed that the Gross-Pitaevskii
equation appears at condition when all dipoles have the same direction which
does not change in time. Comparison of the equation of the electric dipole
evolution with the equation of the magnetization evolution is described.
Dispersion of the collective excitations in the dipolar BEC, either affected or
not affected by the uniform external electric field, is considered using our
method. We show that the evolution of polarization in the BEC leads to the
formation of a novel type of the collective excitations. Detailed description
of the dispersion of collective excitations is presented. We also consider the
process of wave generation in the polarized BEC by means of a monoenergetic
beam of neutral polarized particles. We compute the possibilities of the
generation of Bogoliubov and polarization modes by the dipole beam.Comment: 16 pages, 15 figures. arXiv admin note: substantial text overlap with
arXiv:1106.082
Implications of unitarity and gauge invariance for simplified dark matter models
We show that simplified models used to describe the interactions of dark matter with Standard Model particles do not in general respect gauge invariance and that perturbative unitarity may be violated in large regions of the parameter space. The modifications necessary to cure these inconsistencies may imply a much richer phenomenology and lead to stringent constraints on the model. We illustrate these observations by considering the simplified model of a fermionic dark matter particle and a vector mediator. Imposing gauge invariance then leads to strong constraints from dilepton resonance searches and electroweak precision tests. Furthermore, the new states required to restore perturbative unitarity can mix with Standard Model states and mediate interactions between the dark and the visible sector, leading to new experimental signatures such as invisible Higgs decays. The resulting constraints are typically stronger than the classic constraints on DM simplified models such as monojet searches and make it difficult to avoid thermal overproduction of dark matter
Potential raw material sources for the production of lithic artefacts in western Central Europe – GIS-data for the Rhineland, Westphalia, and the Benelux countries
International audienceSince July 2013, the project D4 of the Collaborative Research Centre 806 at the University of Cologne has dealt with the Mesolithic in western Germany. During the first phase of this research, the primary tasks were to establish a regional chronology for the Middle Stone Age on the one hand, and the mapping of all known sites in the Rhineland and Westphalia regarding the different Mesolithic phases on the other. Since July 2017, the project has focused on mobility, cultural exchange, and human-environment interactions during the Final Palaeolithic, Mesolithic, and Neolithic in Central Europe. Due to the poor conditions of preservation, numerous Palaeolithic and Mesolithic assemblages only contain lithic artefacts. Communication networks and mobility patterns of the hunter-gatherer groups can be deduced from the raw material of these finds for a considerable number of sites. Apart from pottery, lithic artefacts and their resources also illustrate the social and economic networks during the Neolithic. The raw material of knapped artefacts and their potential geological sources offer important information relating to the project's goals. A map of the potential raw material sources for knapped artefacts in comparison with the archaeological finds is the basis for any suggestion about mobility patterns and communication networks. In general, information on geological lithic sources and the archaeological inventories in western Central Europe is far more detailed than for other regions. These data and all the information gathered on lithic raw material sources for western Germany and the Benelux countries allow us to provide a GIS-database using the software QGIS in the form of several maps and data tables with geological and archaeological information as well as detailed descriptions and references. One important result of this paper addresses the reconstruction of lithic raw material catchment areas. Three examples from younger Mesolithic sites show that the more precise petrographic method for identifying lithic raw materials results in much larger catchment areas than traditional macroscopic identification, leading to new considerations for estimating population densities during the later Middle Stone Age
LUMA: A Mapping Assistant for Standardizing the Units of LOINC-Coded Laboratory Tests
The coding system Unified Code for Units of Measure (UCUM) serves the unambiguous electronic communication of physical quantities and their measurements and has faced a slow uptake. Despite being closely related to popular healthcare standards such as LOINC, laboratories still majorly report results using proprietary unit terms. Currently available methods helping users create mappings between their units and UCUM are not flexible and automated enough to be of great use in trying to remedy this. We propose the “LOINC to UCUM Mapping Assistant” (LUMA) as a tool able to overcome the drawbacks of existing approaches while being more accessible even to inexperienced users. By mapping LOINC’s Property axis to representations within UCUM reflecting its semantics, we were able to formalize the association between the two. An HL7 FHIR back-end provides LUMA with UCUM unit recommendations sourced from existing lookup tables simply by providing it with a LOINC code. Additionally, the mappings users created may be used to perform unit conversions from proprietary units to UCUM. The tool was evaluated with five participants from the LADR laboratory network in Germany, who valued the streamlined approach to creating the mappings and particularly emphasized the utility of being able to perform unit conversions within the tool