831 research outputs found
Di-Jet Conical Correlations Associated with Heavy Quark Jets in anti--de Sitter Space/Conformal Field Theory Correspondence
We show that far zone Mach and diffusion wake ``holograms'' produced by
supersonic strings in anti--de Sitter space/conformal field theory (AdS/CFT)
correspondence do not lead to observable conical angular correlations in the
strict supergravity limit if Cooper-Frye hadronization is
assumed. However, a special {\em nonequilibrium} ``neck'' zone near the jet is
shown to produce an apparent sonic boom azimuthal angle distribution that is
roughly independent of the heavy quark's velocity. Our results indicate that a
measurement of the dependence of the away-side correlations on the velocity of
associated identified heavy quark jets at the BNL Relativistic Heavy Ion
Collider and CERN LHC will provide a direct test of the nonperturbative
dynamics involved in the coupling between jets and the strongly-coupled
Quark-Gluon Plasma (sQGP) implied by AdS/CFT correspondence.Comment: 4 pages, 2 figures, version published in Physical Review Letter
Jet Quenching in Non-Conformal Holography
We use our non-conformal holographic bottom-up model for QCD described in
1012.0116 to further study the effect of the QCD trace anomaly on the energy
loss of both light and heavy quarks in a strongly coupled plasma. We compute
the nuclear modification factor for bottom and charm quarks in an
expanding plasma with Glauber initial conditions. We find that the maximum
stopping distance of light quarks in a non-conformal plasma scales with the
energy with a temperature (and energy) dependent effective power.Comment: 4 pages, 1 figure. Proceedings for Quark Matter 201
Anti-Hyperon Enhancement through Baryon Junction Loops
The baryon junction exchange mechanism recently proposed to explain valence
baryon number transport in nuclear collisions is extended to study midrapidity
anti-hyperon production. Baryon junction-anti-junction (J anti-J) loops are
shown to enhance anti-Lambda, anti-Xi, anti-Omega yields as well as lead to
long range rapidity correlations. Results are compared to recent WA97 Pb + Pb
-> Y + anti-Y + X data.Comment: 10 pages, 4 figure
Investigation of lower hybrid physics through power modulation experiments on Alcator C-Mod
Lower hybrid current drive (LHCD) is an attractive tool for off-axis current profile control in magnetically confined tokamak plasmas and burning plasmas (ITER), because of its high current drive efficiency. The LHCD system on Alcator C-Mod operates at 4.6 GHz, with ~ 1 MW of coupled power, and can produce a wide range of launched parallel refractive index (n[subscript ∣∣]) spectra. A 32 chord, perpendicularly viewing hard x-ray camera has been used to measure the spatial and energy distribution of fast electrons generated by lower hybrid (LH) waves. Square-wave modulation of LH power on a time scale much faster than the current relaxation time does not significantly alter the poloidal magnetic field inside the plasma and thus allows for realistic modeling and consistent plasma conditions for different n[subscript ∣∣] spectra. Inverted hard x-ray profiles show clear changes in LH-driven fast electron location with differing n[subscript ∣∣]. Boxcar binning of hard x-rays during LH power modulation allows for ~ 1 ms time resolution which is sufficient to resolve the build-up, steady-state, and slowing-down phases of fast electrons. Ray-tracing/Fokker-Planck modeling in combination with a synthetic hard x-raydiagnostic shows quantitative agreement with the x-ray data for high n[subscript ∣∣] cases. The time histories of hollow x-ray profiles have been used to measure off-axis fast electron transport in the outer half of the plasma, which is found to be small on a slowing down time scale.United States. Dept. of Energy (Award DE-FC02-99ER54512)United States. Dept. of Energy (Award DE-AC02-76CH03073
Application of ECH to the Study of Transport in ITER Baseline Scenario-like Discharges in DIII-D
Recent DIII-D experiments in the ITER Baseline Scenario (IBS) have shown strong increases in fluctuations and correlated reduction of confinement associated with entering the electron-heating-dominated regime with strong electron cyclotron heating (ECH). The addition of 3.2 MW of 110 GHz EC power deposited at ρ~0.42 to IBS discharges with ~3 MW of neutral beam injection causes large increases in low-k and medium-k turbulent density fluctuations observed with Doppler backscatter (DBS), beam emission spectroscopy (BES) and phase-contrast imaging (PCI) diagnostics, correlated with decreases in the energy, particle, and momentum confinement times. Power balance calculations show the electron heat diffusivity χ[subscript e] increases significantly in the mid-radius region 0.4<ρ<0.8, which is roughly the same region where the DBS and BES diagnostics show the increases in turbulent density fluctuations. Confinement of angular momentum is also reduced during ECH. Studies with the TGYRO transport solver show that the model of turbulent transport embodied in the TGLF code quantitatively reproduces the measured transport in both the neutral beam (NB)-only and in the NB plus EC cases. A simple model of the decrease in toroidal rotation with EC power is set forth, which exhibits a bifurcation in the rotational state of the discharge.United States. Dept. of Energy (DE-FC02-04ER54698)United States. Dept. of Energy (DE-FC02-08ER54966)United States. Dept. of Energy (DE-AC03-09CH11466)United States. Dept. of Energy (DE-FG02-04ER54235)United States. Dept. of Energy (DE-FG0289ER53296)United States. Dept. of Energy (DE-FG02-08ER54999)United States. Dept. of Energy (DE-FG02-08ER54984)United States. Dept. of Energy (DE-FG02-04ER54461
The Ter-Mikayelian Effect on QCD Radiative Energy Loss
The color dielectric modification of the gluon dispersion relation in a dense
QCD medium suppresses both the soft and collinear gluon radiation associated
with jet production. We compute both the longitudinal and transverse plasmon
contributions to the zeroth order in opacity radiative energy loss. This QCD
analog of the Ter-Mikayelian effect in QED leads to reduction of the
energy loss of high transverse momentum charm quarks produced in a QCD plasma
with a characteristic Debye mass GeV.Comment: 18 Pages, 16 Figure
Atherosclerosis of the descending aorta predicts cardiovascular events: a transesophageal echocardiography study
PURPOSE: Previous studies have shown that atherosclerosis of the descending aorta detected by transesophageal echocardiography (TEE) is a good marker of coexisting coronary artery disease. The aim of our study was to evaluate whether the presence of atherosclerosis on the descending aorta during TEE has any prognostic impact in predicting cardiovascular events. MATERIAL AND METHODS: The study group consisted of 238 consecutive in-hospital patients referred for TEE testing (135 males, 103 females, mean age 58 +/- 11 years) with a follow up of 24 months. The atherosclerotic lesions of the descending aorta were scored from 0 (no atherosclerosis) to 3 (plaque >5 mm and/or "complex" plaque with ulcerated or mobile parts). RESULTS: Atherosclerosis was observed in 102 patients, (grade 3 in 16, and grade 2 in 86 patients) whereas 136 patients only had an intimal thickening or normal intimal surface. There were 57 cardiovascular events in the follow-up period. The number of events was higher in the 102 patients with (n = 34) than in the 136 patients without atherosclerosis (n = 23, p < 0.01). The frequency of events was in close correlation with the severity of the atherosclerosis of the descending aorta. Fifty percent of the patients with grade 3 experienced cardiovascular events. Excluding patients with subsequent revascularization, the multivariate analysis only left ventricular function with EF < 40% (HR 3.0, CI 1.3–7.1) and TEE atherosclerotic plaque >=2 (HR 2.4, CI 1.0–5.5) predicted hard cardiovascular events. CONCLUSION: Atherosclerosis of the descending aorta observed during transesophageal echocardiography is a useful predictor of cardiovascular events
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