169 research outputs found

    Semileptonic decays of charmed mesons in the effective action of QCD

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    Within the framework of phenomenological Lagrangians we construct the effective action of QCD relevant for the study of semileptonic decays of charmed mesons. Hence we evaluate the form factors of D -> P(0^-) l^+ nu_l at leading order in the 1/N_C expansion and, by demanding their QCD-ruled asymptotic behaviour, we constrain the couplings of the Lagrangian. The features of the model-independent parameterization of form factors provided and their relevance for the analysis of experimental data are pointed out.Comment: 1+24 pages, 1 figure. Updated version. Conclusions unchanged. Accepted for publication in The European Physical Journal

    D^0-D^0(bar) mixing in the weak-gauged U(4)_L x U(4)_R Chiral Lagrangian Model

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    The D^0-D^0(bar) mixing is analyzed in a weak gauged U(4)_L x U(4)_R chiral lagrangian model where the electroweak interaction is introduced as a gauge theory over the meson degrees of freedom. This model allows a particular realization of the G.I.M. mechanism and then could be useful in the study of processes where G.I.M. suppression is effective. As a test of the model we have also analyzed the K^0-K^0(bar) mixing. We find \Delta m_K in good agreement with the experimental result and we show that the D^0-D^0(bar) mixing is very much suppressed in agreement with previous estimates in the Heavy Quark expansion framework.Comment: 14 pages, 2 figures, Latex, minor changes in the writing, final version to be published in Phys. Lett.

    τππ0ντ\tau^{-} \to \pi^{-} \pi^{0} \nu_\tau decay in the extended NJL model

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    The width of the decay τππ0ντ\tau^{-} \to \pi^{-} \pi^{0} \nu_\tau was calculated in the extended NJL model. Contact interaction of WW boson with pion pair as well as the contribution of the ρ\rho mesons in ground and first radial-exited states are taken into account. The sum of the contact diagram and diagram with intermediate ρ\rho meson in the ground state leads to the result which coincides with the result of the vector-dominance model. Our results are in satisfactory agreement with experimental data.Comment: 5 pages, 3 figures, 1 tabl

    Acta Congregationis Prouinciae Hispaniae, Ordinis Praedicatorum, celebratae in Conuentu sancti Dominici Benauentani Die secunda Octobris ... 1677, sub, R. A. P. N. Fr. Ludouico de Villazan ... Prouinciali eiusdem Prouincia

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    Copia digital. Valladolid : Junta de Castilla y León. Consejería de Cultura y Turismo, 2009-2010Sign.: A-H4Port. con orla tip. y esc. xil. de los Dominico

    Relating Andreev Bound States and Supercurrents in Hybrid Josephson Junctions

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    We investigate superconducting quantum interference devices consisting of two highly transmissive Josephson junctions coupled by a superconducting loop, all defined in an epitaxial InAs/Al heterostructure. A novel device design allows for independent measurements of the Andreev bound state spectrum within the normal region of a junction and the resulting current-phase relation. We show that knowledge of the Andreev bound state spectrum alone is enough to derive the independently measured phase dependent supercurrent. On the other hand, the opposite relation does not generally hold true as details of the energy spectrum are averaged out in a critical current measurement. Finally, quantitative understanding of field dependent spectrum and supercurrent require taking into account the second junction in the loop and the kinetic inductance of the epitaxial Al film

    Acta Capituli Prouincialis Prouinciae Hispaniae Ordinis Predicatorum, celebrati in Conuentu Sancti Ildefonsi Regalis Taurensis ... die quinta Maij ... 1675, sub R. A. P. N. Fr. Ludouico de Villazan ... Prouinciali electo eiusdem Prouinciae

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    Copia digital. Valladolid : Junta de Castilla y León. Consejería de Cultura y Turismo, 2009-2010Texto fechado en 1675Sign.: A-E4, [ ]2Port. con orla tip. y esc. xil. de los Dominico

    The Discrepancy Between tau and e+e- Spectral Functions Revisited and the Consequences for the Muon Magnetic Anomaly

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    We revisit the procedure for comparing the pi pi spectral function measured in tau decays to that obtained in e+e- annihilation. We re-examine the isospin-breaking corrections using new experimental and theoretical input, and find improved agreement between the tau- --> pi- pi0 nu_tau branching fraction measurement and its prediction using the isospin-breaking-corrected e+e- --> pi+pi- spectral function, though not resolving all discrepancies. We recompute the lowest order hadronic contributions to the muon g-2 using e+e- and tau data with the new corrections, and find a reduced difference between the two evaluations. The new tau-based estimate of the muon magnetic anomaly is found to be 1.9 standard deviations lower than the direct measurement.Comment: 10 pages, 6 figures, submitted to Eur. Phys. J. C; (v2): Revised version with improved and uniform treatment of tau and e+e- data with HVPTools and a few minor bug fixes; (v3): Final version accepted for publicatio

    The Standard Model Prediction of the Muon Anomalous Magnetic Moment

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    This article reviews and updates the Standard Model prediction of the muon g-2. QED, electroweak and hadronic contributions are presented, and open questions discussed. The theoretical prediction deviates from the present experimental value by 2-3 standard deviations, if e+e- annihilation data are used to evaluate the leading hadronic term.Comment: 30 pages, 8 figures. v2: Updated version to appear in J.Phys.G. Comments and references added, typo corrected in eq.(17

    Evaluation of Haptic Feedback on Bimanually Teleoperated Laparoscopy for Endometriosis Surgery

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    Robotic minimal invasive surgery is gaining acceptance in surgical care. In contrast with the appreciated 3D vision and enhanced dexterity, haptic feedback is not offered. For this reason robotics is not considered beneficial for delicate interventions such the endometriosis. Overall, haptic feedback remains debatable and yet unproven except for some simple scenarios such as Fundamentals of Laparoscopic Surgery exercises. OBJECTIVE: The present work investigates the benefits of haptic feedback on more complex surgical gestures, manipulating delicate tissue through coordination between multiple instruments. Methods: A new training exercise, “Endometriosis Surgery Exercise” (ESE) has been devised approximating the setting for monocular robotic endometriosis treatment. A bimanual bilateral teleoperation setup was designed for laparoscopic laser surgery. Haptic guidance and haptic feedback are respectively offered to the operator. User experiments have been conducted to i) assess the validity of ESE and to ii) examine possible advantages of haptic technology during execution of bimanual surgery. RESULTS: i) Content and face validity of ESE was established by participating surgeons. Surgeons suggested ESE also as a means to train lasering skills, ii) interaction forces on endometriotic tissue were found to be significantly lower when a bilateral controller is used. Collisions between instruments and the environment were less frequent and so were situations marked as potentially dangerous. CONCLUSION: This study provides some promising results suggesting that haptics may offer a distinct advantage in complex robotic interventions were fragile tissue is manipulated. SIGNIFICANCE: Patients need to know whether it should be incorporated. Improved understanding of the value of haptics is important as current commercial surgical robots are widely used but do not offer haptics
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