8,398 research outputs found
Production and optical properties of liquid scintillator for the JSNS experiment
The JSNS (J-PARC Sterile Neutrino Search at J-PARC Spallation Neutron
Source) experiment will search for neutrino oscillations over a 24 m short
baseline at J-PARC. The JSNS inner detector will be filled with 17 tons
of gadolinium-loaded liquid scintillator (LS) with an additional 31 tons of
unloaded LS in the intermediate -catcher and outer veto volumes.
JSNS has chosen Linear Alkyl Benzene (LAB) as an organic solvent because
of its chemical properties. The unloaded LS was produced at a refurbished
facility, originally used for scintillator production by the RENO experiment.
JSNS plans to use ISO tanks for the storage and transportation of the LS.
In this paper, we describe the LS production, and present measurements of its
optical properties and long term stability. Our measurements show that storing
the LS in ISO tanks does not result in degradation of its optical properties.Comment: 7 pages, 4 figures
Efficient nonradiative energy transfer from InGaN/GaN nanopillars to CdSe/ZnS core/shell nanocrystals
Cataloged from PDF version of article.In this study, we propose and demonstrate efficient electron-hole pair injection from InGaN/GaN multiple quantum well nanopillars (MQW-NPs) to CdSe/ZnS core/shell nanocrystal quantum dots (NQDs) via Forster-type nonradiative energy transfer. For that we hybridize blue-emitting MQW-NPs with red-emitting NQDs and the resultant exciton transfer reaches a maximum rate of (0.192 ns)(-1) and a maximum efficiency of 83.0%. By varying the effective bandgap of core/shell NQDs, we conveniently control and tune the excitonic energy transfer rate for these NQD integrated hybrids, and our measured and computed exciton transfer rates are found to be in good agreement for all hybrid cases. (C) 2011 American Institute of Physics
Dissipation in equations of motion of scalar fields
The methods of non-equilibrium quantum field theory are used to investigate
the possibility of representing dissipation in the equation of motion for the
expectation value of a scalar field by a friction term, such as is commonly
included in phenomenological inflaton equations of motion. A sequence of
approximations is exhibited which reduces the non-equilibrium theory to a set
of local evolution equations. However, the adiabatic solution to these
evolution equations which is needed to obtain a local equation of motion for
the expectation value is not well defined; nor, therefore, is the friction
coefficient. Thus, a non-equilibrium treatment is essential, even for a system
that remains close to thermal equilibrium, and the formalism developed here
provides one means of achieving this numerically.Comment: 17 pages, 5 figure
Nonequilibrium perturbation theory for spin-1/2 fields
A partial resummation of perturbation theory is described for field theories
containing spin-1/2 particles in states that may be far from thermal
equilibrium. This allows the nonequilibrium state to be characterized in terms
of quasiparticles that approximate its true elementary excitations. In
particular, the quasiparticles have dispersion relations that differ from those
of free particles, finite thermal widths and occupation numbers which, in
contrast to those of standard perturbation theory evolve with the changing
nonequilibrium environment. A description of this kind is essential for
estimating the evolution of the system over extended periods of time. In
contrast to the corresponding description of scalar particles, the structure of
nonequilibrium fermion propagators exhibits features which have no counterpart
in the equilibrium theory.Comment: 16 pages; no figures; submitted to Phys. Rev.
Baryon Number and Electric Charge Fluctuations in Pb+Pb Collisions at SPS energies
Event-by-event fluctuations of the net baryon number and electric charge in
nucleus-nucleus collisions are studied in Pb+Pb at SPS energies within the HSD
transport model. We reveal an important role of the fluctuations in the number
of target nucleon participants. They strongly influence all measured
fluctuations even in the samples of events with rather rigid centrality
trigger. This fact can be used to check different scenarios of nucleus-nucleus
collisions by measuring the multiplicity fluctuations as a function of
collision centrality in fixed kinematical regions of the projectile and target
hemispheres. The HSD results for the event-by-event fluctuations of electric
charge in central Pb+Pb collisions at 20, 30, 40, 80 and 158 A GeV are in a
good agreement with the NA49 experimental data and considerably larger than
expected in a quark-gluon plasma. This demonstrate that the distortions of the
initial fluctuations by the hadronization phase and, in particular, by the
final resonance decays dominate the observable fluctuations.Comment: 24 pages, 17 figures, to be published in Phys. Rev. C; new results on
electric charge fluctuations in central Pb+Pb collisions at SPS energies have
been adde
Reheating and turbulence
We show that the ''turbulent'' particle spectra found in numerical
simulations of the behavior of matter fields during reheating admit a simple
interpretation in terms of hydrodynamic models of the reheating period. We
predict a particle number spectrum with for Comment: 10 pages, one figure included in tex
Morphology-Dependent Energy Transfer of Polyflorene Nanoparticeles Decorating InGaN/GaN Quantum-Well Nanopillars
Cataloged from PDF version of article.Conjugated polymer nanoparticles (CPNs), prepared in aqueous dispersion from poly[(9,9-bis{3-bromopropyl}fluorenyl-2,7-diyl)-co-(1,4-benzo-{2,1,3}-thiodia- zole)] (PFBT-Br), are incorporated into a nanopillar architecture of InGaN/GaN multiple quantum wells (MQWs) to demonstrate a new organic/inorganic class of nanostructured excitonic model system. This hybrid system enables intimate integration for strong exciton-exciton interactions through nonradiative energy transfer (NRET) between the integrated CPNs and MQW pillars. The NRET of these excitonic systems is systematically investigated at varied temperatures. In these hybrids, InGaN/GaN MQWs serve as the donor of the NRET pair, while immobilized PFBT-Br polymer serves as the acceptor. To understand morphology-dependent NRET, PFBT-Br CPNs coating InGaN/GaN MQWs are made to defold into polymer chains by in situ treatment with a good solvent (THF). The experimental results indicate that NRET is significantly stronger in the case of CPNs compared with their defolded polymer chains. At room temperature, while the NRET efficiency of open polymer chains nanopillar system is only 10%, PFBT-Br CPNs exhibit a substantially higher NRET efficiency of 33% (preserving the total number of polymer molecules). The NRET efficiency of the nanoparticle systems is observed to be 25% at 250 K, 22% at 200 K, 19% at 150 K, and 15% at 100 K. On the other hand, the defolded polymer chains exhibit significantly lower NRET efficiencies of 17% at 250 K, 16% at 200 K, 11% at 150 K, and 5% at 100 K. This work may potentially open up new opportunities for the hybrid organic/inorganic systems where strong excitonic interactions are desired for light generation, light harvesting, and sensing applications
- …