913 research outputs found
Spontaneous emission enhancement of a single molecule by a double-sphere nanoantenna across an interface
We report on two orders of magnitude reduction in the fluorescence lifetime
when a single molecule placed in a thin film is surrounded by two gold
nanospheres across the film interface. By attaching one of the gold particles
to the end of a glass fiber tip, we could control the modification of the
molecular fluorescence at will. We find a good agreement between our
experimental data and the outcome of numerical calculations
Neutron dose rate at the SwissFEL injector test facility: first measurements
At the Paul Scherrer Institute, the new SwissFEL Free Electron Laser facility is currently in the design phase. It is foreseen to accelerate electrons up to a maximum energy of 7 GeV with a pulsed time structure. An injector test facility is operated at a maximum energy of 300 MeV and serves as the principal test and demonstration plant for the SwissFEL project. Secondary radiation is created in unavoidable interactions of the primary beam with beamline components. The resulting ambient dose-equivalent rate due to neutrons was measured along the beamline with different commercially available survey instruments. The present study compares the readings of these neutron detectors (one of them is specifically designed for measurements in pulsed fields). The experiments were carried out in both, a normal and a diagnostic mode of operation of the injecto
Atomic-scale confinement of optical fields
In the presence of matter there is no fundamental limit preventing
confinement of visible light even down to atomic scales. Achieving such
confinement and the corresponding intensity enhancement inevitably requires
simultaneous control over atomic-scale details of material structures and over
the optical modes that such structures support. By means of self-assembly we
have obtained side-by-side aligned gold nanorod dimers with robust
atomically-defined gaps reaching below 0.5 nm. The existence of
atomically-confined light fields in these gaps is demonstrated by observing
extreme Coulomb splitting of corresponding symmetric and anti-symmetric dimer
eigenmodes of more than 800 meV in white-light scattering experiments. Our
results open new perspectives for atomically-resolved spectroscopic imaging,
deeply nonlinear optics, ultra-sensing, cavity optomechanics as well as for the
realization of novel quantum-optical devices
Resonant enhancement of the zero-phonon emission from a color center in a diamond cavity
We demonstrate coupling of the zero-phonon line of individual
nitrogen-vacancy centers and the modes of microring resonators fabricated in
single-crystal diamond. A zero-phonon line enhancement exceeding ten-fold is
estimated from lifetime measurements at cryogenic temperatures. The devices are
fabricated using standard semiconductor techniques and off-the-shelf materials,
thus enabling integrated diamond photonics.Comment: 5 pages, 4 figure
Study of J/psi to p pbar, Lambda Lambdabar and observation of eta_c to Lambda Lambdabar at Belle
We study the baryonic charmonium decays of B mesons, B+ to etac K+ and B+ to
J/psi K+, where the etac and J/psi subsequently decay into a p pbar or Lambda
Lambdabar pair. We measure the J/psi to p pbar, Lambda Lambdabar anisotropy
parameters, alpha_B = -0.60 +- 0.13 +-0.14 (p pbar), -0.44 +- 0.51 +- 0.31
(Lambda Lambdabar) and compare to results from e+e- to J/psi formation
experiments. We also report the first observation of etac to Lambda Lambdabar.
The measured branching fraction is B(etac to Lambda Lambdabar) = (0.87 +0.24
-0.21(stat) +0.09 -0.14(syst) +- 0.27 (PDG)) x 10^-3. This study is based on a
357 fb^-1 data sample recorded on the Upsilon(4S) resonance with the Belle
detector at the KEKB asymmetric-energy e+e- collider.Comment: 8 pages, two figures (4 figure files), an update of hep-ex/0509020
for journal submissio
Charge Asymmetry of Same-Sign Dileptons in - Mixing
We report a measurement of the charge asymmetry for same-sign dileptons in
- mixing, . The data were collected with the Belle
detector at KEKB. Using a data sample of 78 fb recorded at the
resonance and 9 fb recorded at an energy 60 MeV below the
resonance, we measure .Comment: 21 pages, 9 figures, 3 tables, submitted to Physical Review
Time-Dependent CP Asymmetries in B0 -> Ks pi0 gamma transitions
We report measurements of CP violation parameters in B0->Ks pi0 gamma
transitions based on a data sample of 535x10^6 BB pairs collected with the
Belle detector at the KEKB asymmetric-energy e+ e- collider. One neutral B
meson is fully reconstructed in the B0->Ks pi0 gamma mode. The flavor of the
accompanying B meson is identified from its decay products. For a Ks pi0
invariant mass up to 1.8 GeV/c^2, we obtain S = -0.10 +- 0.31 +- 0.07 and A =
-0.20 +- 0.20 +- 0.06. For a Ks pi0 invariant mass near the K*0(892) resonance,
we obtain S = -0.32 +0.36-0.33 +-0.05 and A=-0.20 +-0.24 +-0.05.Comment: 6 pages, 3 figures, accepted by PR
Measurements of Branching Fractions and CP Asymmetries in B-> etah Decays
We report measurements of B to pseudoscalar-pseudoscalar decays with at least
one eta meson in the final state using 140 fb^{-1} of data collected by the
Belle detector at KEKB e^+ e^- collider. We observe the decay B^+-> eta pi^+
and find evidence of B^+-> eta K+; the measured branching fractions are B(B^+->
eta pi^+)=(4.8^{+0.8}_{-0.7}(stat) +- 0.3(sys))*10^{-6} and B(B^+-> eta
K^+)=(2.1 +- 0.6(stat)+- 0.2(sys))*10^{-6}. Their corresponding CP violating
asymmetries are measured to be 0.07+- 0.15 (stat) +- 0.03(sys) for eta pi^+-
and -0.49+- 0.31 (stat) +- 0.07(sys) for eta K^+-. No significant signals are
found for neutral B->eta h decays. We report the following upper limits on
branching fractions at the 90% confidence level: B(B-> eta K^0 < 2.0* 10^{-6},
B(B-> eta pi0) eta eta) <2.0*10^{-6}.Comment: 7 pages, 2 figure
Measurements of Branching Fractions and Polarization in B > K^* rho Decays
We present results of a study of the charmless vector-vector decays B^0 ->
K^{*0} rho^0 and B^+ ->K^{*0} rho^+. The results are based on a 140 fb^{-1}
data sample collected by the Belle detector at the KEKB asymmetric e^+e^-
collider. We obtain the branching fraction B(B^+ -> K^{*0} rho^+)=(6.6 +-
2.2(stat.) +- 0.8 (syst.)) x 10^{-6}, and set upper limits on the branching
fractions B(B^0 -> K^{*0} rho^0) f_0(980)
K^{*0})<5.2 x 10^{-6}. We also perform a helicity analysis of the rho and K^*
vector mesons in the decay B^+ -> K^{*0} rho^+, and obtain the longitudinal
polarization fraction R_0(B^+ -> K^{*0} rho^+)=0.50 +-
0.19(stat.)+0.05-0.07}(syst.).Comment: 11 pages, 4 figures, submitted to ICHEP04, Beijing, Chin
Improved Measurements of Branching Fractions and CP Asymmetries in B-> eta h Decays
We report improved measurements of B decays with an eta meson in the final
state using 492 fb^{-1} of data collected by the Belle detector at the KEKB e^+
e^- collider. We observe the decays B^{+-}-> eta pi^{+-} and B^{+-}-> eta
K^{+-}; the measured branching fractions are Br(B^{+-}-> eta pi^{+-}) = (4.2+-
0.4(stat)+- 0.2(sys))x10^{-6} and Br(B^{+-}-> eta K^{+-}) =
(1.9+-0.3(stat)^{+0.2}_{-0.1}(sys))x10^{-6}. The corresponding CP-violating
asymmetries are measured to be -0.23+- 0.09(stat) +-0.02(sys) for eta pi^{+-}
and -0.39+-0.16(stat)+-0.03(sys) for eta K^{+-}. We also search for B^0-> eta
K^0 decays and set an upper limit of 1.9x10^{-6} at the 90% confidence level.Comment: 7 pages, 3 figure
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