Harko, T., Koivisto, T. S., Lobo, F. S. N., & Olmo, G. J. (2012). Metric-Palatini gravity unifying local constraints and late-time cosmic acceleration. Phys. Rev. D, 85(8), 084016–5pp.
Abstract: We present a novel approach to modified theories of gravity which consists of adding to the Einstein-Hilbert Lagrangian an f(R) term constructed a la Palatini. Using the respective dynamically equivalent scalar-tensor representation, we show that the theory can pass the Solar System observational constraints even if the scalar field is very light. This implies the existence of a long-range scalar field, which is able to modify the cosmological and galactic dynamics but leaves the Solar System unaffected. We also verify the absence of instabilities in perturbations and provide explicit models which are consistent with local tests and lead to the late-time cosmic acceleration.
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Flynn, J. M., Hernandez, E., & Nieves, J. (2012). Triply heavy baryons and heavy quark spin symmetry. Phys. Rev. D, 85(1), 014012–10pp.
Abstract: We study the semileptonic b -> c decays of the lowest-lying triply heavy baryons made from b and c quarks in the limit m(b), m(c) >> Lambda(QCD) and close to the zero-recoil point. The separate heavy-quark spin symmetries strongly constrain the matrix elements, leading to single form factors for ccb -> ccc, bbc -> ccb, and bbb -> bbc baryon decays. We also study the effects on these systems of using a Y-shaped confinement potential, as suggested by lattice QCD results for the interaction between three static quarks.
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Dib, C., Helo, J. C., Hirsch, M., Kovalenko, S., & Schmidt, I. (2012). Heavy sterile neutrinos in tau decays and the MiniBooNE anomaly. Phys. Rev. D, 85(1), 011301–4pp.
Abstract: Current results of the MiniBooNE experiment show excess events that indicate neutrino oscillations, but only if one goes beyond the standard 3 family scenario. Recently a different explanation of the events has been given, not in terms of oscillations but by the production and decay of a massive sterile neutrino with large transition magnetic moment. We study the effect of such a sterile neutrino in the rare decays tau(-) -> mu(-)mu(+)pi(-)nu and tau(-) -> mu(-)mu(+)e(-)nu nu. We find that searches for these decays, featuring displaced vertices between the mu(-) and the other charged particles, constitute reliable tests for the existence of the sterile neutrino proposed to explain the MiniBooNE anomaly. These searches could be done with already existing experimental data.
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BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., & Oyanguren, A. (2012). Measurement of the semileptonic branching fraction of the B(s) meson. Phys. Rev. D, 85(1), 011101–9pp.
Abstract: We report a measurement of the inclusive semileptonic branching fraction of the B(s) meson using data collected with the BABAR detector in the center-of-mass energy region above the Y(4S) resonance. We use the inclusive yield of phi mesons and the phi yield in association with a high-momentum lepton to perform a simultaneous measurement of the semileptonic branching fraction and the production rate of B(s) mesons relative to all B mesons as a function of center-of-mass energy. The inclusive semileptonic branching fraction of the B(s) meson is determined to be B(B(s) -> l nu X) = 9.5(-2.0)(+2.5)(stat)(-1.9)(+1.1)(syst)% where l indicates the average of e and mu.
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Noguera, S., & Scopetta, S. (2012). Eta-photon transition form factor. Phys. Rev. D, 85(5), 054004–12pp.
Abstract: The eta-photon transition form factor is evaluated in a formalism based on a phenomenological description at low values of the photon virtuality, and a QCD-based description at high photon virtualities, matching at a scale Q(0)(2). The high photon virtuality description makes use of a distribution amplitude calculated in the Nambu-Jona-Lasinio model with Pauli-Villars regularization at the matching scale Q(0)(2), and QCD evolution from Q(0)(2) to higher values of Q(2). A good description of the available data is obtained. The analysis indicates that the recent data from the BABAR collaboration on pion and eta transition form factor can be well reproduced, if a small contribution of higher twist is added to the dominant twist-two contribution at the matching scale Q(0)(2).
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