Summary of the CMS potential for the Higgs boson discovery

The European Physical Journal C - This work summarizes the studies for the Higgs boson searches in CMS at the LHC collider. The main discovery channels are presented and the potential is given for...     

Emission spectrum of a dressed exciton-biexciton complex in a semiconductor quantum dot

The photoluminescence spectrum of a single quantum dot was recorded as a secondary resonant laser optically dressed either the vacuum-to-exciton or the exciton-to-biexciton transitions. High-resolution polarization-resolved measurements using a scanning Fabry-Pérot interferometer reveal splittings of the linearly polarized fine-structure states that are nondegenerate in an asymmetric quantum dot. These splittings manifest as either triplets or doublets and depend sensitively on laser intensity and detuning. Our approach realizes complete resonant control of a multiexcitonic system in emission, which can be either pulsed or continuous wave, and offers direct access to the emitted photons.     

Development of diamond-based X-ray detection for high-flux beamline diagnostics

High‐quality single‐crystal and polycrystalline chemical‐vapor‐deposition diamond detectors with platinum contacts have been tested at the white‐beam X28C beamline at the National Synchrotron Light Source under high‐flux conditions. The voltage dependence of these devices has been measured under both DC and pulsed‐bias conditions, establishing the presence or absence of photoconductive gain in each device. Linear response consistent with the theoretically determined ionization energy has been achieved over eleven orders of magnitude when combined with previous low‐flux studies. Temporal measurements with single‐crystal diamond detectors have resolved the nanosecond‐scale pulse structures of both the NSLS and the APS. Prototype single‐crystal quadrant detectors have provided the ability to simultaneously resolve the X‐ray beam position and obtain a quantitative measurement of the flux.     

Nonlinear resonant ultrasound spectroscopy (NRUS) applied to damage assessment in bone

Nonlinear resonant ultrasound spectroscopy (NRUS) is a resonance-based technique exploiting the significant nonlinear behavior of damaged materials. In NRUS, the resonant frequency(ies) of an object is studied as a function of the excitation level. As the excitation level increases, the elastic nonlinearity is manifest by a shift in the resonance frequency. This study shows the feasibility of this technique for application to damage assessment in bone. Two samples of bovine cortical bone were subjected to progressive damage induced by application of mechanical cycling. Before cycling commenced, and at each step in the cycling process, NRUS was applied for damage assessment. For independent assessment of damage, high-energy x-ray computed tomography imaging was performed but was only useful in identifying the prominent cracks. As the integral quantity of damage increased, NRUS revealed a corresponding increase in the nonlinear response. The measured change in nonlinear response is much more sensitive than the change in linear modulus. The results suggest that NRUS could be a potential tool for micro-damage assessment in bone. Further work must be carried out for a better understanding of the physical nature of damaged bone and for the ultimate goal of the challenging in vivo implementation of the technique.     

Fluctuation probes of quark deconfinement

A classical and quantum mechanical generalized second law of thermodynamics in cosmology implies constraints on the effective equation of state of the universe in the form of energy conditions, obeyed by many known cosmological solutions, forbids certain cosmological singularities, and is compatible with entropy bounds. This second law is based on the conjecture that causal boundaries and not only event horizons have geometric entropies proportional to their area. In string cosmology the second law provides new information about nonsingular solutions.     

Viscous heating and the stability of newtonian and viscoelastic taylor-couette flows

The effects of viscous heating on the stability of Taylor-Couette flow were investigated through flow visualization experiments for Newtonian and viscoelastic fluids. For highly viscous Newtonian fluids, viscous heating drives a transition to a new, oscillatory mode of instability at a critical Reynolds number significantly below that at which the inertial transition is observed in isothermal flows. The effects of viscous heating may explain the discrepancies between the observed and predicted critical conditions and the symmetry of the disturbance flow for viscoelastic instabilities.     

Complex dynamic behavior of fluctuating smectic- A films as studied by scattering with coherent X-rays

Coherent dynamic x-ray scattering has been used to study the thermally excited layer fluctuations in freely suspended smectic films of the compound 4O.8. Using 8-keV x rays and films with a thickness around 0.3 &mgr;m we resolve relaxation times down to a few &mgr;s. A combination of damped and oscillatory behavior is observed for the layer undulations, which can be attributed to inertial effects. These are due to the surface contribution to the free energy which cannot be disregarded for thin films.