Oceanic lithosphere and asthenosphere: The thermal and mechanical structure

A coupled thermal and mechanical solid state model of the oceanic lithosphere and asthenosphere is presented. The model includes vertical conduction of heat with a temperature dependent thermal conductivity, horizontal and vertical advection of heat, viscous dissipation or shear heating, and linear or nonlinear deformation mechanisms with temperature and pressure dependent constitutive relations between shear stress and strain rate. A constant horizontal velocity u sub 0 and temperature t sub 0 at the surface and zero horizontal velocity and constant temperature t sub infinity at great depth are required. In addition to numerical values of the thermal and mechanical properties of the medium, only the values of u sub 0, t sub 0 and t sub infinity are specified. The model determines the depth and age dependent temperature horizontal and vertical velocity, and viscosity structures of the lithosphere and asthenosphere. In particular, ocean floor topography, oceanic heat flow, and lithosphere thickness are deduced as functions of the age of the ocean floor

Thermal and mechanical structure of the upper mantle: A comparison between continental and oceanic models

Temperature, velocity, and viscosity profiles for coupled thermal and mechanical models of the upper mantle beneath continental shields and old ocean basins show that under the continents, both tectonic plates and the asthenosphere, are thicker than they are beneath the oceans. The minimum value of viscosity in the continental asthenosphere is about an order of magnitude larger than in the shear zone beneath oceans. The shear stress or drag underneath continental plates is also approximately an order of magnitude larger than the drag on oceanic plates. Effects of shear heating may account for flattening of ocean floor topography and heat flux in old ocean basins

A new method for extracting the bottom quark Yukawa coupling at the CERN Large Hadron Collider

We propose a new method for measuring the H -> bb rate at the CERN LHC in a manner which would allow extraction of the b quark Yukawa coupling. Higgs boson production in purely electroweak WHjj events is calculated. The Standard Model signal rate including decays W -> l nu and H -> bb is 11 fb for M_H = 120 GeV. It is possible to suppress the principal backgrounds, Wbbjj and ttjj, to approximately the level of the signal. As the top quark Yukawa coupling does not appear in this process, it promises a reliable extraction of g_Hbb in the context of the Standard Model or some extensions, such as the MSSM.Comment: added background, updated/added references, additional comment

Ozone-depleting substances (ODSs) and related chemicals

The amended and adjusted Montreal Protocol continues to be successful at reducing emissions and atmospheric abundances of most controlled ozone-depleting substances (ODSs).Global Ozone Research and Monitoring Projec

The UARS microwave limb sounder version 5 data set: Theory, characterization, and validation

Nitric acid (HNO3) is a major player in processes controlling the springtime depletion of polar ozone. It is the main constituent of the Polar Stratospheric Clouds (PSCs) and a primary reservoir for reactive nitrogen. Potential variations in the stratospheric circulation and temperature may alter the extent and duration of PSCs activity, influencing the future ozone levels significantly. Monitoring HNO3 and its long-term variability, especially in polar region, is then crucial for better understanding issues related to ozone decline and expected recovery. In this study we present an intercomparison between ground based HNO3 measurements, carried out by means of the Ground-Based Millimeter-wave Spectrometer (GBMS), and two satellite data sets produced by the two NASA/JPL Microwave Limb Sounder (MLS) experiments. In particular, we compare UARS MLS measurements (1991-1999) with those carried out by the GBMS at South Pole, Antarctica (90°S), Fall of 1993 and 1995. A similar intercomparison is made between Aura MLS HNO3 observations (2004 - to date) and GBMS measurements obtained during the period February 2004 - March 2007, at the mid-latitudes/high altitudes station of Testa Grigia (45.9° N, 7.7° E, elev. 3500 m), and during polar winters 2008/09 and 2009/2010 at Thule Air Base (76.5°N 68.8°W), Greenland. We assess systematic differences between GBMS and both UARS and Aura HNO3 data sets at seven potential temperature levels (θ) spanning the range 465 – 960 K. The UARS data set advected to the South Pole shows a low bias, within 20% for all θ levels but the 960 K, with respect to GBMS measurements. A very good agreement, within 5%, is obtained between Aura and GBMS observations at Testa Grigia, while larger differences, possibly due to latitude dependent effects, are observed over Thule. These differences are under further investigations but a preliminary comparison over Thule among MLS v3, GBMS, and ACE-FTS measurements suggests that GBMS measurements carried out during winter 2009 might not be reliable. These comparisons have been performed in the framework of the NASA JPL GOZCARDS project, which is aimed at developing a long-term, global data record of the relevant stratospheric constituents in the context of ozone decline. GBMS has been selected in GOZCARDS since its HNO3 dataset, although sampling different latitudes in different years, is the only one spanning a sufficiently long time interval for cross-calibrating HNO3 measurements by the UARS and Aura MLS experiments

First Report of the Simulation Optimization Group

This is the first report of the ATLAS Simulation Optimization Group, established in June of 2007. This article justifies the selected Geant4 version, physics list, and range cuts to be used by the default ATLAS simulation for initial data taking and beyond. The current status of several projects, including detector description, simulation validation, studies of additional Geant4 parameters, and cavern background, are reported

Dimensionless Coupling of Bulk Scalars at the LHC

We identify the lowest-dimension interaction which is possible between Standard Model brane fields and bulk scalars in 6 dimensions. The lowest-dimension interaction is unique and involves a trilinear coupling between the Standard Model Higgs and the bulk scalar. Because this interaction has a dimensionless coupling, it depends only logarithmically on ultraviolet mass scales and heavy physics need not decouple from it. We compute its influence on Higgs physics at ATLAS and identify how large a coupling can be detected at the LHC. Besides providing a potentially interesting signal in Higgs searches, such couplings provide a major observational constraint on 6D large-extra-dimensional models with scalars in the bulk.Comment: 20 page

Higgs Bosons Strongly Coupled to the Top Quark

Several extensions of the Standard Model require the burden of electroweak symmetry breaking to be shared by multiple states or sectors. This leads to the possibility of the top quark interacting with a scalar more strongly than it does with the Standard Model Higgs boson. In top-quark condensation this possibility is natural. We also discuss how this might be realized in supersymmetric theories. The properties of a strongly coupled Higgs boson in top-quark condensation and supersymmetry are described. We comment on the difficulties of seeing such a state at the Tevatron and LEPII, and study the dramatic signatures it could produce at the LHC. The four top quark signature is especially useful in the search for a strongly coupled Higgs boson. We also calculate the rates of the more conventional Higgs boson signatures at the LHC, including the two photon and four lepton signals, and compare them to expectations in the Standard Model.Comment: 18 pages, latex, 9 figure