3,308 research outputs found

    Semileptonic KL Decays at NA48

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    Preliminary results on KL->pi e nu(gamma) decays collected by the NA48 detector at the CERN SPS are reported. Using a sample of 6.8 X 10^6 reconstructed events BR(Ke3) = 0.4010+-0.0028+-0.0035 was obtained. From the branching ratio the value of |Vus|= 0.2187+-0.0028 was extracted. The same data sample has provided also a high precision measurement of the slope lambda+ of the form factor of the Ke3 decay. Investigating the Ke3gamma decay, from a sample of 18977 reconstructed events, BR(Ke3gamma)/BR(Ke3) = (0.964+-0.008+0.012-0.011)% was determined.Comment: 4 pages, 2 figures. To appear in the proceedings of the Vth Rencontres du Vietnam, Particle Physics and Astrophysics, Hanoi, Vietnam, August 5-11, 200

    A study of nuclear effects in ν\nu interactions with the NOMAD detector

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    Nuclear effects in \numucc interactions with carbon nuclei have been studied by using backward going protons and π−\pi^-. Detailed analyses, of the momentum distributions and of the production rates, have been carried out in order to understand the mechanism producing these particles. The backward proton data have been compared with the predictions of the reinteraction and the short range correlation models.Comment: 8 pages, 7 figures, to be published in Proc. of NUINT01, The First International Workshop on Neutrino-Nucleus Interactions in the Few GeV Region; December 13-16 2001, KEK Tsukuba, Japa

    Laser-Accelerated proton beams as diagnostics for cultural heritage

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    This paper introduces the first use of laser-generated proton beams as diagnostic for materials of interest in the domain of Cultural Heritage. Using laser-accelerated protons, as generated by interaction of a high-power short-pulse laser with a solid target, we can produce proton-induced X-ray emission spectroscopies (PIXE). By correctly tuning the proton flux on the sample, we are able to perform the PIXE in a single shot without provoking more damage to the sample than conventional methodologies. We verify this by experimentally irradiating materials of interest in the Cultural Heritage with laser-accelerated protons and measuring the PIXE emission. The morphological and chemical analysis of the sample before and after irradiation are compared in order to assess the damage provoked to the artifact. Montecarlo simulations confirm that the temperature in the sample stays safely below the melting point. Compared to conventional diagnostic methodologies, laser-driven PIXE has the advantage of being potentially quicker and more efficien

    Laser-Generated Proton Beams for High-Precision Ultra-Fast Crystal Synthesis

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    We present a method for the synthesis of micro-crystals and micro-structured surfaces using laseraccelerated protons. In this method, a solid surface material having a low melting temperature is irradiated with very-short laser-generated protons, provoking in the ablation process thermodynamic conditions that are between the boiling and the critical point. The intense and very quick proton energy deposition (in the ns range) induces an explosive boiling and produces microcrystals that nucleate in a plasma plume composed by ions and atoms detached from the laser-irradiated surface. The synthesized particles in the plasma plume are then deposited onto a cold neighboring, non-irradiated, solid secondary surface. We experimentally verify the synthesizing methods by depositing low-meltingmaterial microcrystals - such as gold - onto nearby silver surfaces and modeling the proton/matter interaction via a Monte Carlo code, confrming that we are in the above described thermodynamic conditions. Morphological and crystallinity measurements indicate the formation of gold octahedral crystals with dimensions around 1.2 μm, uniformly distributed onto a silver surface with dimensions in the tens of mm2. This laser-accelerated particle based synthesis method paves the way for the development of new material synthesis using ultrashort laser-accelerated particle beams

    Model for the spatio-temporal intermittency of the energy dissipation in turbulent flows

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    Modeling the intermittent behavior of turbulent energy dissipation processes both in space and time is often a relevant problem when dealing with phenomena occurring in high Reynolds number flows, especially in astrophysical and space fluids. In this paper, a dynamical model is proposed to describe the spatio-temporal intermittency of energy dissipation rate in a turbulent system. This is done by using a shell model to simulate the turbulent cascade and introducing some heuristic rules, partly inspired by the well known pp-model, to construct a spatial structure of the energy dissipation rate. In order to validate the model and to study its spatially intermittency properties, a series of numerical simulations have been performed. These show that the level of spatial intermittency of the system can be simply tuned by varying a single parameter of the model and that scaling laws in agreement with those obtained from experiments on fully turbulent hydrodynamic flows can be recovered. It is finally suggested that the model could represent a useful tool to simulate the spatio-temporal intermittency of turbulent energy dissipation in those high Reynolds number astrophysical fluids where impulsive energy release processes can be associated to the dynamics of the turbulent cascade.Comment: 22 pages, 9 figure
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