3,886 research outputs found

    Off-diagonal structure of neutrino mass matrix in see-saw mechanism and electron-muon-tau lepton universality

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    By a simple extension of the standard model in which (eμτe-\mu -\tau ) universality is not conserved, we present a scenario within the framework of see-saw mechanism in which the neutrino mass matrix is strictly off-diagonal in the flavor basis. We show that a version of this scenario can accomodate the atmospheric νμντ\nu_\mu -\nu_\tau neutrino oscillations and νμνe\nu_\mu -\nu_e oscillations claimed by the LSND collaboration. PACS: 14.60.Pq; 14.60.St;13.15.+gComment: 5 pages, Revtex, 1 figure: The model accomodate another version which explains atmospheric neutrino data and the observed solar neutrino oscillations (large angle solution). In the previous version the value of \lambda parameter is changed to the expected one. This version now accomodates LSND result and solar neutrino oscillations (small angle MSW solution

    The Control System for a new Pixel Detector at the sLHC

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    For the upgrade of the LHC, the sLHC (super Large Hadron Collider), a new ATLAS Pixel Detector is planned, which will require a completely new control system. To reduce the material budget new power distribution schemes are under investigation, where the active power conversion is located inside the detector volume. Such a new power supply system will need new control strategies. Parts of the control must be located closer to the loads. The minimization of mass, the demand for less cables and the re-use of the outer existing services are the main restrictions to the design of the control system. The requirements of the DCS (Detector Control System) and a first concept will be presented. We will focus on a control chip which necessarily has to be implemented in the new system. A setup of discrete components has been built up to investigate and verify the chip’s requirements. We report on the status of the work

    Upgrade of the BOC for the ATLAS Pixel Insertable B-Layer

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    The phase 1 upgrade of the ATLAS [1] pixel detector will be done by inserting a fourth pixel layer together with a new beampipe into the recent three layer detector. This new detector, the Insertable B-Layer (IBL) should be integrated into the recent pixel system with as few changes in services as possible, but deliver some advantages over the recent system. One of those advantages will be a new data transmission link from the detector modules to the off-detector electronics, requiring a re-design of the electro-optical converters on the off-detector side. First ideas of how to implement those, together with some ideas to reduce cost by increasing the systems throughput are discussed

    Detector Control System of the ATLAS Insertable B-Layer

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    soumis à publicationTo improve tracking robustness and precision of the ATLAS inner tracker an additional fourth pixel layer is foreseen, called Insertable B-Layer (IBL). It will be installed between the innermost present Pixel layer and a new smaller beam pipe and is presently under construction. As, once installed into the experiment, no access is available, a highly reliable control system is required. It has to supply the detector with all entities required for operation and protect it at all times. Design constraints are the high power density inside the detector volume, the sensitivity of the sensors against heatups, and the protection of the front end electronics against transients. We present the architecture of the control system with an emphasis on the CO2 cooling system, the power supply system and protection strategies. As we aim for a common operation of pixel and IBL detector, the integration of the IBL control system into the Pixel one will be discussed as well

    Improved limits on nuebar emission from mu+ decay

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    We investigated mu+ decays at rest produced at the ISIS beam stop target. Lepton flavor (LF) conservation has been tested by searching for \nueb via the detection reaction p(\nueb,e+)n. No \nueb signal from LF violating mu+ decays was identified. We extract upper limits of the branching ratio for the LF violating decay mu+ -> e+ \nueb \nu compared to the Standard Model (SM) mu+ -> e+ nue numub decay: BR < 0.9(1.7)x10^{-3} (90%CL) depending on the spectral distribution of \nueb characterized by the Michel parameter rho=0.75 (0.0). These results improve earlier limits by one order of magnitude and restrict extensions of the SM in which \nueb emission from mu+ decay is allowed with considerable strength. The decay \mupdeb as source for the \nueb signal observed in the LSND experiment can be excluded.Comment: 10 pages, including 1 figure, 1 tabl

    Neutrino-nucleus reactions on ^{12}C and ^{16}O

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    Exclusive and inclusive (νμ,μ),(νe,e)(\nu_\mu, \mu^-), (\nu_e, e^-) cross-sections and μ\mu^--capture rates are calculated for ^{12}C and ^{16}O using the consistent random phase approximation (RPA) and pairing model. After a pairing correction is introduced to the RPA results the flux-averaged theoretical (νμ,μ),(νe,e)(\nu_\mu, \mu^-), (\nu_e, e^-) cross-sections and μ\mu^--capture rates in 12^{12}C are in good agreement with experiment. In particular when one takes into account the experimental error bars, the recently measured range of values for the (νμ,μ)(\nu_\mu, \mu^-) cross-section is in agreement with the present theoretical results. Predictions of (νμ,μ)(\nu_\mu, \mu^-) and (νe,e)(\nu_e, e^-) cross-sections in ^{16}O are also presented.Comment: 13 pages, Revte

    Leptonic Decays of Heavy Quarks on the Lattice

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    The status of lattice calculations of heavy-light decay constants and of the BB parameter BBB_B is reviewed. After describing the lattice approach to heavy quark systems, the main results are discussed, with special emphasis on the systematic errors in present lattice calculations. A detailed analysis of the continuum limit for decay constants is performed. The implications of lattice results on studies of CP violation in the Standard Model are discussed.Comment: Invited review to be published in Int. J. Mod. Phys. A, 63 pages, LaTeX, ijmpa1.sty (included), 8 postscript figure

    Shell-model calculations of neutrino scattering from 12C

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    Neutrino reaction cross-sections, (νμ,μ)(\nu_\mu,\mu^-), (νe,e)(\nu_e,e^-), μ\mu-capture and photoabsorption rates on 12^{12}C are computed within a large-basis shell-model framework, which included excitations up to 4ω4\hbar\omega. When ground-state correlations are included with an open pp-shell the predictions of the calculations are in reasonable agreement with most of the experimental results for these reactions. Woods-Saxon radial wave functions are used, with their asymptotic forms matched to the experimental separation energies for bound states, and matched to a binding energy of 0.01 MeV for unbound states. For comparison purposes, some results are given for harmonic oscillator radial functions. Closest agreement between theory and experiment is achieved with unrestricted shell-model configurations and Woods-Saxon radial functions. We obtain for the neutrino-absorption inclusive cross sections: σˉ=13.8×1040\bar{\sigma} = 13.8 \times 10^{-40} cm2^2 for the (νμ,μ)(\nu_{\mu},\mu^{-}) decay-in-flight flux in agreement with the LSND datum of (12.4±1.8)×1040(12.4 \pm 1.8) \times 10^{-40} cm2^2; and σˉ=12.5×1042\bar{\sigma} = 12.5 \times 10^{-42} cm2^2 for the (νe,e)(\nu_{e},e^{-}) decay-at-rest flux, less than the experimental result of (14.4±1.2)×1042(14.4 \pm 1.2) \times 10^{-42} cm2^2.Comment: 19 pages. ReVTeX. No figure

    Coherent pion production in neutrino nucleus collision in the 1 GeV region

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    We calculate cross sections for coherent pion production in nuclei induced by neutrinos and antineutrinos of the electron and muon type. The analogies and differences between this process and the related ones of coherent pion production induced by photons, or the (p,n) and (3He,t)(^3 He, t) reactions are discussed. The process is one of the several ones occurring for intermediate energy neutrinos, to be considered when detecting atmospheric neutrinos. For this purpose the results shown here can be easily extrapolated to other energies and other nuclei.Comment: 13 pages, LaTex, 8 post-script figures available at [email protected]