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Strong longitudinal color-field effects in pp collisions at energies available at the CERN Large Hadron Collider
We study the effect of strong longitudinal color fields (SCF) in p + p reactions up to Large Hadron Collider (LHC) energies in the framework of the hijing/BB (v2.0) model that combines (collinear factorized) perturbative quantum chromodynamics multiple minijet production with soft longitudinal string excitation and hadronization. The default vacuum string tension, {kappa}{sub 0} = 1 GeV/fm, is replaced by an effective energy-dependent string tension, {kappa}(s)={kappa}{sub 0}(s/s{sub 0}){sup 0.06} that increases monotonically with center-of-mass energy. The exponent {lambda}=0.06 is found sufficient to reproduce well the energy dependence of multiparticle observables in the Relativistic Heavy Ion Collider, Tevatron, as well as recent LHC data. This exponent is half of that predicted by the color glass saturation (CGC) model, {lambda}{sub CGC}=0.115, where gluon fusion multiparticle production mechanisms are assumed. In hijing/BB (v2.0), the rapid growth of dN{sub ch}/d{eta} with energy is due to the interplay of copious minijet production with increasing SCF contributions. The large (strange) baryon-to-meson ratios measured at Tevatron energies are well described. A significant enhancement of these ratios is predicted up to the highest LHC energy (14 TeV). The effect of JJ loops and SCF on baryon-antibaryon asymmetry, and its relation to baryon number transport, is also discussed.
Measurement of color flow in t t ¯ events from p p ¯ collisions at s = 1.96 TeV
Not Available
Efficient Blue Phosphorescent OLEDs with Improved Stability and Color Purity through Judicious Triplet Exciton Management
Abstract Highly efficient and stable blue phosphorescent organic light‐emitting diodes are achieved by employing a step‐wise graded doping of platinum(II) 9‐(pyridin‐2‐yl)‐2‐(9‐(pyridin‐2‐yl)‐9 H ‐carbazol‐2‐yloxy)‐9 H ‐carbazole (PtNON) in a device setting. A device employing PtNON demonstrates a high peak external quantum efficiency (EQE) of 17.4% with an estimated LT 70 lifetime of over 1330 h at a brightness of 1000 cd m −2 . PtNON is then investigated as a “triplet sensitizer” in an alternating donor–acceptor doped emissive layer to further improve the device emission color purity by carefully managing an efficient Förster resonant energy transfer from PtNON to 2,5,8,11‐tetra‐ tert ‐butylperylene as a selected acceptor material. Thus, such OLED devices demonstrate an EQE of 16.9% with color coordinates of (0.16, 0.25) and an estimated luminance (LT 70 ) lifetime of 628 h at a high brightness of 1000 cd m −2 .
Edge Dislocations Induce Improved Photocatalytic Efficiency of Colored TiO2
Titanium oxide is the most widely used material for photocatalytic applications due to its low cost and environmental friendliness. One of the grand challenges to improve its energy conversion efficiency is to utilize more visible light while inhibiting the recombination of photo-generated electrons and holes. We use a one-step hydro-solvothermal method to obtain colored ultra-fine nanowires of rutile and nanoparticles of anatase with edge dislocations, which induced broadened visible solar absorption (400-900 nm) and improved photocatalytic efficiency up to 1.8 times that of rutile or anatase without defects. Enhanced photocatalytic activity of these structures is demonstrated by photodegrading methylene blue measurements under simulated solar light irradiation. Results show the existence of Ti3+, induced by edge dislocations, and subsequent electronic band structure-property relationships. This work highlights a strategy for generating sufficient desired defects in TiO2 nanostructures, leading to broadened visible solar absorption and improved photocatalytic efficiency under visible light irradiation.
Thermodynamics of lattice QCD with 2 flavours of color-sextet quarks : a model of walking/conformal technicolor.
QCD with two flavors of massless color-sextet quarks is considered as a model for conformal/walking technicolor. If this theory possesses an infrared fixed point, as indicated by 2-loop perturbation theory, it is a conformal (unparticle) field theory. If, on the other hand, a chiral condensate forms on the weak-coupling side of this would-be fixed point, the theory remains confining. The only difference between such a theory and regular QCD is that there is a range of momentum scales over which the coupling constant runs very slowly (walks). In this first analysis, we simulate the lattice version of QCD with two flavors of staggered quarks at finite temperatures on lattices of temporal extent N{sub t} = 4 and 6. The deconfinement and chiral-symmetry restoration couplings give us a measure of the scales associated with confinement and chiral-symmetry breaking. We find that, in contrast to what is seen with fundamental quarks, these transition couplings are very different. {beta} = 6/g{sup 2} for each of these transitions increases significantly from N{sub t} = 4 and N{sub t} = 6 as expected for the finite-temperature transitions of an asymptotically free theory. This suggests a walking rather than a conformal behavior, in contrast to what is observed with Wilson quarks. In contrast to what is found for fundamental quarks, the deconfined phase exhibits states in which the Polyakov loop is oriented in the directions of all three cube roots of unity. At very weak coupling the states with complex Polyakov loops undergo a transition to a state with a real, negative Polyakov loop.
Probabilistic density function method for nonlinear dynamical systems driven by colored noise
Not Available
Correlating dynamic microstructure to observed color in electrophoretic displays via in situ small-angle x-ray scattering
Electrophoretic deposition (EPD) is an industrially relevant and scalable technique used to form particle deposits from colloidal suspensions. Highly concentrated particle suspensions generally prevent real-time in situ microscopy observations which limit the characterization of EPD films to ex situ, or postprocessed, laboratory techniques. For dynamic systems, such as tunable amorphous photonic crystals (APCs), only reversible deposits are formed during the EPD process. Since reversible deposits cannot be characterized with standard ex situ methods, the particle-particle and particle-field interactions that govern the displayed color and crystallinity of these systems are not well understood. In this paper, we present in situ small-angle x-ray scattering and UV-Vis techniques for measuring both the structural and optical response of an APC under applied electric fields. Furthermore, we also develop a computational model based on colloidal interactions to explain the observed change in the interparticle spacing of APCs due to the applied electric field which correlates to displayed color. Ultimately, this work provides a new in situ characterization method that could be expanded for other dynamic, tunable colloidal systems.
Evidence for the onset of color transparency in ρ 0 electroproduction off nuclei
We have measured the nuclear transparency of the incoherent diffractive A(e,e'ρ 0 ) process in 12 C and 56 Fe targets relative to 2 H using a 5 GeV electron beam. The nuclear transparency, the ratio of the produced {rho}{sup 0}'s on a nucleus relative to deuterium, which is sensitive to ρA interaction, was studied as function of the coherence length (I c ), a lifetime of the hadronic fluctuation of the virtual photon, and the four-momentum transfer squared (Q 2 ). Thus, while the transparency for both 12 C and 56 Fe showed no I c dependence, a significant Q 2 dependence was measured, which is consistent with calculations that included the color transparency effects.
Two-color spatial and temporal temperature measurements using a streaked soft x-ray imager
A dual-channel streaked soft x-ray imager has been designed and used on high energy-density physics experiments at the National Ignition Facility. This streaked imager creates two images of the same x-ray source using two slit apertures and a single shallow angle reflection from a nickel mirror. Thin filters are used to create narrow band pass images at 510 eV and 360 eV. When measuring a Planckian spectrum, the brightness ratio of the two images can be translated into a color-temperature, provided that the spectral sensitivity of the two images is well known. To reduce uncertainty and remove spectral features in the streak camera photocathode from this photon energy range, a thin 100 nm CsI on 50 nm Al streak camera photocathode was implemented. Provided that the spectral shape is well-known, then uncertainties on the spectral sensitivity limits the accuracy of the temperature measurement to approximately 4.5% at 100 eV.
Probability Density Function Method for Langevin Equations with Colored Noise
We present a novel method to derive closed-form, computable PDF equations for Langevin systems with colored noise. The derived equations govern the dynamics of joint or marginal probability density functions (PDFs) of state variables, and rely on a so-called Large-Eddy-Diffusivity (LED) closure. We demonstrate the accuracy of the proposed PDF method for linear and nonlinear Langevin equations, describing the classical Brownian displacement and dispersion in porous media.
The Light-Front Schrödinger Equation and Determination of the Perturbative QCD Scale from Color Confinement
The valence Fock-state wavefunctions of the light-front QCD Hamiltonian satisfy a relativistic equation of motion with an effective confining potential U which systematically incorporates the effects of higher quark and gluon Fock states. If one requires that the effective action which underlies the QCD Lagrangian remains conformally invariant and extends the formalism of de Alfaro, Fubini and Furlan to light front Hamiltonian theory, the potential U has a unique form of a harmonic oscillator potential, and a mass gap arises. The result is a nonperturbative relativistic light-front quantum mechanical wave equation which incorporates color confinement and other essential spectroscopic and dynamical features of hadron physics, including a massless pion for zero quark mass and linear Regge trajectories with the same slope in the radial quantum number n and orbital angular momentum L. Only one mass parameter κ appears. Light-front holography thus provides a precise relation between the bound-state amplitudes in the fifth dimension of AdS space and the boost-invariant light-front wavefunctions describing the internal structure of hadrons in physical space-time. We also show how the mass scale κ underlying confinement and hadron masses determines the scale Λ {ovr MS} controlling the evolution of the perturbative QCD coupling. The relation between scales is obtained by matching the nonperturbative dynamics, as described by an effective conformal theory mapped to the light-front and its embedding in AdS space, to the perturbative QCD regime computed to four-loop order. The result is an effective coupling defined at all momenta. The predicted value Λ {ovr MS }=0.328±0.034 GeV is in agreement with the world average 0.339±0.010 GeV. The analysis applies to any renormalization scheme.