1,505 research outputs found
Efficient unidirectional nanoslit couplers for surface plasmons
Plasmonics is based on surface plasmon polariton (SPP) modes which can be
laterally confined below the diffraction limit, thereby enabling ultracompact
optical components. In order to exploit this potential, the fundamental
bottleneck of poor light-SPP coupling must be overcome. In established SPP
sources (using prism, grating} or nanodefect coupling) incident light is a
source of noise for the SPP, unless the illumination occurs away from the
region of interest, increasing the system size and weakening the SPP intensity.
Back-side illumination of subwavelength apertures in optically thick metal
films eliminates this problem but does not ensure a unique propagation
direction for the SPP. We propose a novel back-side slit-illumination method
based on drilling a periodic array of indentations at one side of the slit. We
demonstrate that the SPP running in the array direction can be suppressed, and
the one propagating in the opposite direction enhanced, providing localized
unidirectional SPP launching.Comment: 13 pages, 4 figure
Quantum Imaging
We provide a brief overview of the newly born field of quantum imaging, and
discuss some concepts that lie at the root of this field.Comment: 8 pages, 19 figure
First results from NA60 on low mass muon pair production in In-In collisions at 158 GeV/nucleon
The NA60 experiment at the CERN SPS studies dimuon production in
proton-nucleus and nucleus-nucleus collisions. The combined information from a
novel vertex telescope made of radiation-tolerant silicon pixel detectors and
from the muon spectrometer previously used in NA50 allows for a precise
measurement of the muon vertex and a much improved dimuon mass resolution. We
report on first results from the data taken for Indium-Indium collisions at 158
AGeV/nucleon in 2003, concentrating on a subsample of about 370 000 muon pairs
in the mass range GeV/. The light vector mesons and
are completely resolved, with a mass resolution of about 23 MeV/
at the . The transverse momentum spectra of the are measured over
the continuous range GeV/c; the inverse slope parameter of
the spectra is found to increase with centrality, with an average value of
MeV.Comment: 9 pages, 6 figures. Plenary talk, SQM2004 conference, Cape Town,
South Africa 15-20 September, 2004. To be published in Journal of Physics G:
Nuclear and Particle Physic
NA60 results on thermal dimuons
The NA60 experiment at the CERN SPS has measured muon pairs with
unprecedented precision in 158A GeV In-In collisions. A strong excess of pairs
above the known sources is observed in the whole mass region 0.2<M<2.6 GeV. The
mass spectrum for M<1 GeV is consistent with a dominant contribution from
pi+pi- -> rho -> mu+mu- annihilation. The associated rho spectral function
shows a strong broadening, but essentially no shift in mass. For M>1 GeV, the
excess is found to be prompt, not due to enhanced charm production, with
pronounced differences to Drell-Yan pairs. The slope parameter Teff associated
with the transverse momentum spectra rises with mass up to the rho, followed by
a sudden decline above. The rise for M<1 GeV is consistent with radial flow of
a hadronic emission source. The seeming absence of significant flow for M>1 GeV
and its relation to parton-hadron duality is discussed in detail, suggesting a
dominantly partonic emission source in this region. A comparison of the data to
the present status of theoretical modeling is also contained. The accumulated
empirical evidence, including also a Planck-like shape of the mass spectra at
low pT and the lack of polarization, is consistent with a global interpretation
of the excess dimuons as thermal radiation. We conclude with first results on
omega in-medium effects.Comment: 10 pages, 12 figures, submitted to Eur. Phys. J.
Information encoded in a network of inflammation proteins predicts clinical outcome after myocardial infarction
HIV-1 Infection in Cyprus, the Eastern Mediterranean European Frontier: A Densely Sampled Transmission Dynamics Analysis from 1986 to 2012
Since HIV-1 treatment is increasingly considered an effective preventionstrategy, it is important to study local HIV-1 epidemics to formulate tailored preventionpolicies. The prevalence of HIV-1 in Cyprus was historically low until 2005. To investigatethe shift in epidemiological trends, we studied the transmission dynamics of HIV-1 in Cyprususing a densely sampled Cypriot HIV-1 transmission cohort that included 85 percent ofHIV-1-infected individuals linked to clinical care between 1986 and 2012 based on detailedclinical, epidemiological, behavioral and HIV-1 genetic information. Subtyping andtransmission cluster reconstruction were performed using maximum likelihood and Bayesianmethods, and the transmission chain network was linked to the clinical, epidemiological andbehavioral data. The results reveal that for the main HIV-1 subtype A1 and B sub-epidemics,young and drug-naïve HIV-1-infected individuals in Cyprus are driving the dynamics of thelocal HIV-1 epidemic. The results of this study provide a better understanding of thedynamics of the HIV-1 infection in Cyprus, which may impact the development of preventionstrategies. Furthermore, this methodology for analyzing densely sampled transmissiondynamics is applicable to other geographic regions to implement effective HIV-1 preventionstrategies in local settings
Large and robust electrical spin injection into GaAs at zero magnetic field using an ultrathin CoFeB/MgO injector
We demonstrate a large electrical spin injection into GaAs at zero magnetic
field thanks to an ultrathin perpendicularly magnetized CoFeB contact of a few
atomic planes (1.2 nm). The spin-polarization of electrons injected into GaAs
was examined by the circular polarization of electroluminescence from a Spin
Light Emitting Diode with embedded InGaAs/GaAs quantum wells. The
electroluminescence polarization as a function of the magnetic field closely
traces the out-of-plane magnetization of the CoFeB/MgO injector. A circular
polarization degree of the emitted light as large as 20% at 25 K is achieved at
zero magnetic field. Moreover the electroluminescence circular polarization is
still about 8% at room temperature.Comment: *Corresponding author: [email protected]
Search for CP Violation in the Decay Z -> b (b bar) g
About three million hadronic decays of the Z collected by ALEPH in the years
1991-1994 are used to search for anomalous CP violation beyond the Standard
Model in the decay Z -> b \bar{b} g. The study is performed by analyzing
angular correlations between the two quarks and the gluon in three-jet events
and by measuring the differential two-jet rate. No signal of CP violation is
found. For the combinations of anomalous CP violating couplings, and , limits of \hat{h}_b < 0.59h^{\ast}_{b} < 3.02$ are given at 95\% CL.Comment: 8 pages, 1 postscript figure, uses here.sty, epsfig.st
Search for the glueball candidates f0(1500) and fJ(1710) in gamma gamma collisions
Data taken with the ALEPH detector at LEP1 have been used to search for gamma
gamma production of the glueball candidates f0(1500) and fJ(1710) via their
decay to pi+pi-. No signal is observed and upper limits to the product of gamma
gamma width and pi+pi- branching ratio of the f0(1500) and the fJ(1710) have
been measured to be Gamma_(gamma gamma -> f0(1500)). BR(f0(1500)->pi+pi-) <
0.31 keV and Gamma_(gamma gamma -> fJ(1710)). BR(fJ(1710)->pi+pi-) < 0.55 keV
at 95% confidence level.Comment: 10 pages, 3 figure
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