1,699 research outputs found
Commissioning of the ATLAS Liquid Argon Calorimeters
A selection of ATLAS liquid argon (LAr) calorimeter commissioning studies is
presented. It includes a coherent noise study, a measurement of the quality of
the ionization pulse shape prediction, and energy and time reconstruction
analyses with cosmic and single beam signals.Comment: Proceedings from the CIPANP 2009 Conferenc
Dark Matter in B-L Extended MSSM Models
We analyze the dark matter problem in the context of supersymmetric
U(1)_{B-L} model. In this model, the lightest neutalino can be the B-L gaugino
widetilde {Z}_{B-L} or the extra Higgsinos widetilde{chi}_{1,2} dominated. We
compute the thermal relic abundance of these particles and show that, unlike
the LSP in MSSM, they can account for the observed relic abundance with no
conflict with other phenomenological constraints. The prospects for their
direct detection, if they are part of our galactic halo, are also discussed.Comment: 11 pages, 9 figures. Published versio
Electroweak Symmetry Breaking and Proton Decay in SO(10) SUSY-GUT with TeV W_R
In a recent paper, we proposed a new class of supersymmetric SO(10) models
for neutrino masses where the TeV scale electroweak symmetry is SU(2)_L\times
SU(2)_R\times U(1)_{B-L} making the associated gauge bosons W_R and Z'
accessible at the Large Hadron Collider. We showed that there exists a domain
of Yukawa coupling parameters and symmetry breaking patterns which give an
excellent fit to all fermion masses including neutrinos. In this sequel, we
discuss an alternative Yukawa pattern which also gives good fermion mass fit
and then study the predictions of both models for proton lifetime. Consistency
with current experimental lower limits on proton life time require the squark
masses of first two generations to be larger than ~ 1.2 TeV. We also discuss
how one can have simultaneous breaking of both SU(2)_R\times U(1)_{B-L} and
standard electroweak symmetries via radiative corrections.Comment: 31 pages, 5 figures, 4 tables
Impacts of the Mount Pinatubo eruption on ENSO in the GEOS seasonal-to-subseasonal forecasting system
The eruption of Mount Pinatubo in June 1991 introduced a perturbation of the Earth's global energy budget by increasing the stratospheric aerosol loading by an order of magnitude, with effects on the global climate. In this presentation we analyze the effects of the Mt. Pinatubo eruption on the seasonal forecast performed with Goddard Earth Observing System Seasonal-to Subseasonal (GEOS-S2S) system, an Earth System Model that includes an interactive ocean and a bulk aerosol model coupled to radiation. We performed 10-member ensembles for the year after the eruption (June 1991-May 1992) at ~0.5 horizontal resolution, with and without the inclusion of the Mt. Pinatubo eruption. In GEOS-S2S, the eruption leads to ta strengthening of El Nino peaking in January 1992. The strengthening is mainly due to the weakening of the trade winds, which is caused by a attening of the temperature gradient across the Pacic due to a differential response to the volcanic forcing between the central and eastern Pacic (ocean-dynamical thermostat). This response largely depends on the assumed size for the volcanic aerosols. Indeed, we performed simulations assuming a volcanic aerosol effective radius of 0.35 m (similar to tropospheric aerosol, and the default in GEOS) and 0.6 m (closer to observations of volcanic aerosol from Pinatubo-sized eruptions). We nd that in the latter case the tropical radiative forcing is lower, since smaller aerosols scatter shortwave radiation more eciently than larger ones. Accordingly, the impact on ENSO is not statistically signicant when a larger and more realistic particle radius is assumed
Charm meson resonances in decays
Motivated by recent experimental results we reconsider semileptonic decays within a model which combines heavy quark symmetry and
properties of the chiral Lagrangian. We include excited charm meson states,
some of them recently observed, in our Lagrangian and determine their impact on
the charm meson semileptonic form factors. We find that the inclusion of
excited charm meson states in the model leads to a rather good agreement with
the experimental results on the shape of the form factor. We
also calculate branching ratios for all decays.Comment: 9 pages, 4 figures; minor corrections, added some discussion, version
as publishe
Possible improvements on the mass of the tau neutrino using leptonic decays
We show how a very accurate measurement of the branching ratios of the
leptonic decay modes of the mesons can lead to a significant
improvement in the mass limit for the tau neutrino.Comment: 1 typo in Eq.2 correcte
PALEOZOIC HIDROTHERMAL SYSTEM IN THE ILLINOIS BASIN AND ITS EFFECT ON DISTRIBUTION AND RANK OF HYDROCARBONS
La Cuenca de Illinois en el Medio Oeste de Estados Unidos es una cuenca intracratonica que contiene reserves sustanciales de carbón en el Paleozoico Superior. El rango de dicho carbón es alto, considerando que el carbón no fue enterrado profundamente. Un re-análisis de las temperaturas al tiempo de carbonización (utilizando reflectancia de la vitrinita, conodontes, e inclusiones de fluidos) indica diferentes patrones. En la parte sur de la cuenca, las paleogeotermas (perfiles de temperatura vs. profundidad) son irregulares. En la parte central, hay un incremento abrupto en el gradiente cerca al nivel del contacto Pensilvaniano/Misisipiano. En la parte norte, el gradiente es paralelo a la geoterma actual. Estos resultados son compatibles con un modelo en el cual fluidos calientes, migrando de sur a norte a través de acuíferos carboníferos, introdujeron calor al carbón. Estos fluidos pudieron haber sido calentados por intrusiones Pérmicas al sur. Modelamiento preliminar de elementos finitos, utilizando Basin2, demuestra que la migración de tales fluidos pudo producir los rangos de carbón observados. Estudios preliminares de catodoluminiscencia encuentran dolomita barroca como evidencia adicional de migración de fluidos hidrotermales. Las inclusiones de fluidos en las venas indican que las temperaturas de los fluidos eran cercanas a los 100°C.
Palabras claves: hidrotermal, carbón, rango, gradiente, paleotermómetro
The Illinois Basin of the Midwestern United States is an intracratonic basin containing substantial coal reserves in Upper Carboniferous strata. The rank of this coal is anomalously high, considering that the coal was not buried deeply. A reexamination of paleotemperatures at the time of coalification (using vitrinite reflectance; conodonts; and fluid inclusions) indicates distinct patterns. In the southern portion of the basin, paleogeotherms (profiles of paleotemperature vs. depth) are irregular. In the central part of the basin, there is an abrupt increase in the geothermal gradient at the level of the Pennsylvanian/Mississippian contact. In the northern portion of the basin, the gradient is parallel to present-day geotherm. These results are compatible with a model in which hot fluids, migrating from south to north through aquifers within the Carboniferous, introduced heat to the coal. These fluids may have been warmed by Permian intrusions at the south of the Illinois basin. Preliminary finite-element models of groundwater flow, produced using Basin2, demonstrate that such fluid migration could produce temperatures necessary to produce coal ranks observed. Preliminary cathodoluminescence study found baroque dolomite in cements, further evidence of hydrothermal-fluid migration. Fluid inclusions in the veins indicate fluid temperatures were close to 100°C.
Key words: hydrothermal, coal, rank, gradient, paleothermomete
Remote sensing of cloud sides of deep convection: towards a three-dimensional retrieval of cloud particle size profiles
International audienceThe cloud scanner sensor is a central part of a recently proposed satellite remote sensing concept ? the three-dimensional (3-D) cloud and aerosol interaction mission (CLAIM-3D) combining measurements of aerosol characteristics in the vicinity of clouds and profiles of cloud microphysical characteristics. Such a set of collocated measurements will allow new insights in the complex field of cloud-aerosol interactions affecting directly the development of clouds and precipitation, especially in convection. The cloud scanner measures radiance reflected or emitted by cloud sides at several wavelengths to derive a profile of cloud particle size and thermodynamic phase. For the retrieval of effective size a Bayesian approach was adopted and introduced in a preceding paper. In this paper the potential of the approach, which has to account for the complex three-dimensional nature of cloud geometry and radiative transfer, is tested in realistic cloud observing situations. In a fully simulated environment realistic cloud resolving modelling provides complex 3-D structures of ice, water, and mixed phase clouds, from the early stage of convective development to mature deep convection. A three-dimensional Monte Carlo radiative transfer is used to realistically simulate the aspired observations. A large number of cloud data sets and related simulated observations provide the database for an experimental Bayesian retrieval. An independent simulation of an additional cloud field serves as a synthetic test bed for the demonstration of the capabilities of the developed retrieval techniques
Double Type-II Seesaw, Baryon Asymmetry and Dark Matter for Cosmic e^\pm Excesses
We construct a new realization of type-II seesaw for neutrino masses and
baryon asymmetry by extending the standard model with one light and two heavy
singlet scalars besides one Higgs triplet. The heavy singlets pick up small
vacuum expectation values to give a suppressed trilinear coupling between the
triplet and doublet Higgs bosons after the light singlet drives the spontaneous
breaking of lepton number. The Higgs triplet can thus remain light and be
accessible at the LHC. The lepton number conserving decays of the heavy
singlets can generate a lepton asymmetry stored in the Higgs triplet to account
for the matter-antimatter asymmetry in the Universe. We further introduce
stable gauge bosons from a hidden sector, which obtain masses and annihilate
into the Higgs triplet after spontaneous breaking of the associated non-Abelian
gauge symmetry. With Breit-Wigner enhancement, the stable gauge bosons can
simultaneously explain the relic density of dark matter and the cosmic
positron/electron excesses.Comment: 9 pages, 4 figures, minor rewording, final PRD version (in Press
PALEOZOIC HIDROTHERMAL SYSTEM IN THE ILLINOIS BASIN AND ITS EFFECT ON DISTRIBUTION AND RANK OF HYDROCARBONS
La Cuenca de Illinois en el Medio Oeste de Estados Unidos es una cuenca intracratonica que contiene reserves sustanciales de carbón en el Paleozoico Superior. El rango de dicho carbón es alto, considerando que el carbón no fue enterrado profundamente. Un re-análisis de las temperaturas al tiempo de carbonización (utilizando reflectancia de la vitrinita, conodontes, e inclusiones de fluidos) indica diferentes patrones. En la parte sur de la cuenca, las paleogeotermas (perfiles de temperatura vs. profundidad) son irregulares. En la parte central, hay un incremento abrupto en el gradiente cerca al nivel del contacto Pensilvaniano/Misisipiano. En la parte norte, el gradiente es paralelo a la geoterma actual. Estos resultados son compatibles con un modelo en el cual fluidos calientes, migrando de sur a norte a través de acuíferos carboníferos, introdujeron calor al carbón. Estos fluidos pudieron haber sido calentados por intrusiones Pérmicas al sur. Modelamiento preliminar de elementos finitos, utilizando Basin2, demuestra que la migración de tales fluidos pudo producir los rangos de carbón observados. Estudios preliminares de catodoluminiscencia encuentran dolomita barroca como evidencia adicional de migración de fluidos hidrotermales. Las inclusiones de fluidos en las venas indican que las temperaturas de los fluidos eran cercanas a los 100°C.
Palabras claves: hidrotermal, carbón, rango, gradiente, paleotermómetro
The Illinois Basin of the Midwestern United States is an intracratonic basin containing substantial coal reserves in Upper Carboniferous strata. The rank of this coal is anomalously high, considering that the coal was not buried deeply. A reexamination of paleotemperatures at the time of coalification (using vitrinite reflectance; conodonts; and fluid inclusions) indicates distinct patterns. In the southern portion of the basin, paleogeotherms (profiles of paleotemperature vs. depth) are irregular. In the central part of the basin, there is an abrupt increase in the geothermal gradient at the level of the Pennsylvanian/Mississippian contact. In the northern portion of the basin, the gradient is parallel to present-day geotherm. These results are compatible with a model in which hot fluids, migrating from south to north through aquifers within the Carboniferous, introduced heat to the coal. These fluids may have been warmed by Permian intrusions at the south of the Illinois basin. Preliminary finite-element models of groundwater flow, produced using Basin2, demonstrate that such fluid migration could produce temperatures necessary to produce coal ranks observed. Preliminary cathodoluminescence study found baroque dolomite in cements, further evidence of hydrothermal-fluid migration. Fluid inclusions in the veins indicate fluid temperatures were close to 100°C.
Key words: hydrothermal, coal, rank, gradient, paleothermomete
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