Explore the vast range of titles available.

The transition to turbulence in a rotating boundary layer is analysed via direct numerical simulation (DNS) in an annular cavity made of two parallel corotating discs of finite radial extent, with a forced inflow at the hub and free outflow at the rim. In a former numerical investigation (Viaud, Serre & Chomaz J. Fluid Mech., vol. 598, 2008, pp. 451–464) realized in a sectorial cavity of azimuthal extent $2\\lrm{\\pi} / 68$, we have established the existence of a primary bifurcation to nonlinear global mode with angular phase velocity and radial envelope coherent with the so-called elephant mode theory. The former study has demonstrated the subcritical nature of this primary bifurcation with a base flow that keeps being linearly stable for all Reynolds numbers studied. The present work investigates the stability of this elephant mode by extending the cavity both in the radial and azimuthal direction. When the Reynolds number based on the forced throughflow is increased above a threshold value for the existence of the nonlinear global mode, a large-amplitude impulsive perturbation gives rise to a self-sustained saturated wave with characteristics identical to the 68-fold global elephant mode obtained in the smaller cavity. This saturated wave is itself globally unstable and a second front appears in the lee of the primary where small-scale instability develops. These secondary instabilities are identical for the $2\\lrm{\\pi} / 68$ and the $2\\lrm{\\pi} / 4$ long sectorial cavities, indicating that transition involves a Floquet mode of zero azimuthal wavenumber. This secondary instability leads to a very disorganized state, defining the transition to turbulence. The observed transition to turbulence linked to the secondary instability of a global mode confirms, for the first time on a real flow, the possibility of a direct transition to turbulence through an elephant mode cascade, a scenario that was up to now only observed on the Ginzburg–Landau model.

In 1956 Reines & Cowan discovered the neutrino using a liquid scintillator detector. The neutrinos interacted with the scintillator, producing light that propagated across transparent volumes to surrounding photo-sensors. This approach has remained one of the most widespread and successful neutrino detection technologies used since. This article introduces a concept that breaks with the conventional paradigm of transparency by confining and collecting light near its creation point with an opaque scintillator and a dense array of optical fibres. This technique, called LiquidO, can provide high-resolution imaging to enable efficient identification of individual particles event-by-event. A natural affinity for adding dopants at high concentrations is provided by the use of an opaque medium. With these and other capabilities, the potential of our detector concept to unlock opportunities in neutrino physics is presented here, alongside the results of the first experimental validation. Liquid scintillator detectors have been used to study neutrinos ever since their discovery in 1956. The authors introduce an opaque scintillator detector concept for future neutrino experiments with increased capacity for particle identification and a natural affinity for doping.

Spectral direct numerical simulations (DNS) are carried out for a source–sink flow in an annular cavity between two co-rotating disks. When the Reynolds number based on the forced inflow is increased, a self-sustained crossflow instability of finite amplitude is observed. We show that this nonlinear global mode is made up of a front located at the upstream boundary of the absolutely unstable domain, followed by a saturated spiral mode, and that its properties are in good agreement with results of the local stability theory. This structure is characteristic of the so-called elephant mode of Pier & Huerre (J. Fluid Mech. vol. 435, 2001, p. 145). The global bifurcation is subcritical since only large-amplitude initial perturbations are found to trigger the elephant mode. Small-amplitude perturbations induce a long-lasting transient growth but lead eventually to a damped linear global mode, showing that non-parallel effects counteract the absolute instability and restabilize the flow. A similar linear global stabilization due to non-parallel effects has been found in the case of the flow above a single rotating disk. For the single-disk geometry, the existence of an elephant mode would imply, together with results of Davies & Carpenter (2003) a subcritical global instability, which has not yet been demonstrated. Although the present geometry differs from the single-disk case, the existence of a subcritical global bifurcation is now established, allowing a precise analysis of the transition scenarios.

This paper describes the LUMI project which aims at providing fast, reliable and absolute luminosity measurements at the modified DAφNE interaction point in Frascati for testing the new \"crabbed waist\" scheme. We present a description of the experimental setup (two luminometers, LUMI1 and LUMI2), the simulation framework developped for this project and summarize the results and performances.

The yields and production rates of the radioisotopes $^{9}$ Li and $^{8}$ He created by cosmic muon spallation on $^{12}$ C, have been measured by the two detectors of the Double Chooz experiment. The identical detectors are located at separate sites and depths, which means that they are subject to different muon spectra. The near (far) detector has an overburden of ∼120 m.w.e. (∼300 m.w.e.) corresponding to a mean muon energy of 32.1 ± 2.0 GeV (63.7 ± 5.5 GeV). Comparing the data to a detailed simulation of the $^{9}$ Li and $^{8}$ He decays, the contribution of the $^{8}$ He radioisotope at both detectors is found to be compatible with zero. The observed $^{9}$ Li yields in the near and far detectors are 5.51 ± 0.51 and 7.90 ± 0.51, respectively, in units of 10 $^{−8}$ μ $^{−1}$ g $^{−1}$ cm $^{2}$ . The shallow overburdens of the near and far detectors give a unique insight when combined with measurements by KamLAND and Borexino to give the first multi-experiment, data driven relationship between the $^{9}$ Li yield and the mean muon energy according to the power law$ Y = {Y}_0{\\left(\\left\\langle {E}_{\\mu}\\right\\rangle /1\\ GeV\\right)}^{\\overline{\\alpha}} $, giving$ \\overline{\\alpha} = 0.72 \\pm 0.06 $and Y $_{0}$= (0.43 ± 0.11) × 10 $^{−8}$ μ $^{−1}$ g $^{−1}$ cm $^{2}$ . This relationship gives future liquid scintillator based experiments the ability to predict their cosmogenic $^{9}$ Li background rates.

Associated production of bottomonia and open charm hadrons inppcollisions at√s̅=7and8 TeV is observed using data corresponding to an integrated luminosity of 3 fb⁻¹accumulated with the LHCb detector. The observation of five combinations,Υ(1S)D⁰ ,Υ(2S)D⁰ ,Υ(1S)D⁺ ,Υ(2S)D⁺andΥ(1S)D⁺_(s) , is reported. Production cross-sections are measured forΥ(1S)D⁰andΥ(1S)D⁺pairs in the forward region. The measured cross-sections and the differential distributions indicate the dominance of double parton scattering as the main production mechanism. This allows a precise measurement of the effective cross-section for double parton scattering.

The first model-independent measurement of the charm mixing parameters in the decayD⁰ → K_(S) π⁺ π⁻is reported, using a sample ofppcollision data recorded by the LHCb experiment, corresponding to an integrated luminosity of 1.0 fb ⁻¹at a centre-of-mass energy of 7 TeV. The measured values are eqnarray* x &=& (+0.86 0.53 0.17) 10⁻2, y &=& (+0.03 0.46 0.13) 10⁻2, eqnarray* where the first uncertainties are statistical and include small contributions due to the external input for the strong phase measured by the CLEO collaboration, and the second uncertainties are systematic. The results are consistent with the current world averages.

Production cross-sections of prompt charm mesons are measured with the first data from$pp$collisions at the LHC at a centre-of-mass energy of$13\\,\\mathrm{TeV}$ . The data sample corresponds to an integrated luminosity of$4.98 \\pm 0.19\\,\\mathrm{pb}^{-1}$collected by the LHCb experiment. The production cross-sections of$D^{0}$ ,$D^{+}$ ,$D_{s}^{+}$ , and$D^{*+}$mesons are measured in bins of charm meson transverse momentum,$p_{\\mathrm{T}}$ , and rapidity,$y$ , and cover the range$0 < p_{\\mathrm{T}} < 15\\,\\mathrm{GeV}/c$and$2.0 < y < 4.5$ . The ratios of the integrated cross-sections between charm mesons agree with previously measured fragmentation fractions. The inclusive$c\\overline{c}$cross-section within the range of$0 < p_{\\mathrm{T}} < 8\\,\\mathrm{GeV}/c$is found to be \\[ (pp ccX) = 2940 3 180 160\\, \\] where the uncertainties are due to statistical, systematic and fragmentation fraction uncertainties, respectively.

TheB_(s)⁰ → J/ψ φ φdecay is observed inppcollision data corresponding to an integrated luminosity of 3 fb ⁻¹recorded by the LHCb detector at centre-of-mass energies of 7 TeV and 8 TeV. This is the first observation of this decay channel, with a statistical significance of 15 standard deviations. The mass of theB_(s)⁰meson is measured to be5367.08 ± 0.38 ± 0.15MeV/c ² . The branching fraction ratio𝓑(B_(s)⁰ → J/ψ φ φ)/𝓑(B_(s)⁰ → J/ψ φ)is measured to be0.0115 ± 0.0012 ^(+0.0005)_(-0.0009) . In both cases, the first uncertainty is statistical and the second is systematic. No evidence for non-resonantB_(s)⁰ → J/ψ φ K⁺ K⁻orB_(s)⁰ → J/ψ K⁺ K⁻ K⁺ K⁻decays is found.