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 B0B^0-Bˉ0\bar{B}^0 Mixing

We report a measurement of the charge asymmetry for same-sign dileptons in $B^0$-$\bar{B}^0$ mixing, $A_{\rm sl}$. The data were collected with the Belle detector at KEKB. Using a data sample of 78 fb$^{-1}$ recorded at the $\Upsilon(4S)$ resonance and 9 fb$^{-1}$ recorded at an energy 60 MeV below the resonance, we measure $A_{\rm sl} = (-1.1 \pm 7.9(\text{stat}) \pm 7.0(\text{sys}))\times 10^{-3}$.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