3,891 research outputs found

    Mixing of pseudoscalar mesons and isospin symmetry breaking

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    Mixing of the pseudoscalar mesons is discussed in the quark-flavor basis with the hypothesis that the basis decay constants follow the pattern of particle state mixing. The divergences of the axial vector currents which embody the axial vector anomaly, combined with this hypothesis provide a calculational scheme for the parameters describing the mixing of the pion, eta and eta' mesons. Phenomenological applications of this mixing scheme are presented with particular interest focussed on isospin symmetry breaking in QCD estimated as eta and eta' admixtures to the pion. In contrast to previous work a possible difference in the basis decay constants f_u and f_d is considered and consequences of this potentially large effect on the strength of isospin symmetry breaking is discussed.Comment: 10 pages, (using LATEX with w-ijmpa.sty), invited talk presented at MESON 2004, 8th Intern. Workshop on Meson Production, Properties and Interaction

    The study of BJ/Ψη()B\to J/\Psi \eta^{(\prime)} decays and determination of ηη\eta-\eta^{\prime} mixing angle

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    We study BJ/Ψη()B\to J/\Psi \eta^{(\prime)} decays and suggest two methods to determine the ηη\eta-\eta^{\prime} mixing angle. We calculate not only the factorizable contribution in QCD facorization scheme but also the nonfactorizable hard spectator corrections in pQCD approach. We get the branching ratio of BJ/ΨηB\to J/\Psi \eta which is consistent with recent experimental data and predict the branching ratio of BJ/ΨηB\to J/\Psi \eta^{\prime} to be 7.59×1067.59\times 10^{-6}. Two methods for determining ηη\eta-\eta^{\prime} mixing angle are suggested in this paper. For the first method, we get the ηη\eta-\eta^{\prime} mixing angle to be about 13.1-13.1^{\circ}, which is in consistency with others in the literature. The second method depends on less parameters so can be used to determine the ηη\eta-\eta^{\prime} mixing angle with better accuracy but needs, as an input, the branching ratio for BJ/ΨηB\to J/\Psi \eta^{\prime}which should be measured in the near future.Comment: 16pages,4figure

    See-Saw Masses for Quarks and Leptons in SU(5)

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    We build on a recent paper by Grinstein, Redi and Villadoro, where a see-saw like mechanism for quark masses was derived in the context of spontaneously broken gauged flavour symmetries. The see-saw mechanism is induced by heavy Dirac fermions which are added to the Standard Model spectrum in order to render the flavour symmetries anomaly-free. In this letter we report on the embedding of these fermions into multiplets of an SU(5) grand unified theory and discuss a number of interesting consequences.Comment: 15 pages, 4 figures (v3: outline restructured, modified mechanism to cancel anomalies

    Mixing and Decay Constants of Pseudoscalar Mesons: The Sequel

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    We present further tests and applications of the new eta-eta' mixing scheme recently proposed by us. The particle states are decomposed into orthonormal basis vectors in a light-cone Fock representation. Because of flavor symmetry breaking the mixing of the decay constants can be identical to the mixing of particle states at most for a specific choice of this basis. Theoretical and phenomenological considerations show that the quark flavor basis has this property and allows, therefore, for a reduction of the number of mixing parameters. A detailed comparison with other mixing schemes is also presented.Comment: 9 page

    Role of "Intrinsic Charm" in Semi-Leptonic B-Meson Decays

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    We discuss the role of so-called "intrinsic-charm" operators in semi-leptonic B-meson decays, which appear first at order 1/m_b^3 in the heavy quark expansion. We show by explicit calculation that -- at scales mu <= m_c -- the contributions from "intrinsic-charm" effects can be absorbed into short-distance coefficient functions multiplying, for instance, the Darwin term. Then, the only remnant of "intrinsic charm" are logarithms of the form ln(m_c^2/m_b^2), which can be resummed by using renormalization-group techniques. As long as the dynamics at the charm-quark scale is perturbative, alpha_s(m_c) << 1, this implies that no additional non-perturbative matrix elements aside from the Darwin and the spin-orbit term have to be introduced at order 1/m_b^3. Hence, no sources for additional hadronic uncertainties have to be taken into account. Similar arguments may be made for higher orders in the 1/m_b expansion.Comment: 14 pages, 1 figure, uses slashed.sty, slight modifications to match published versio

    Light-cone sum rules: A SCET-based formulation

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    We describe the construction of light-cone sum rules (LCSRs) for exclusive BB-meson decays into light energetic hadrons from correlation functions within soft-collinear effective theory (SCET). As an example, we consider the SCET sum rule for the BπB \to \pi transition form factor at large recoil, including radiative corrections from hard-collinear loop diagrams at first order in the strong coupling constant.Comment: LaTex, 4 pages, 2 eps figures. Talk given at QCD05, 12th International QCD Conference, 4-9th July 2005, Montpellier, Franc

    Supersymmetric contributions to B --> K pi in the view of recent experimental result

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    Supersymmetric contributions to the branching ratios and CP asymmetries of B--> K pi decays are analyzed in the view of recent experimental measurements. We show that supersymmetry can still provide a natural solution to the apparent discrepancy between theses results and the standard model expectations. We emphasize that chargino contributions may enhance the electroweak penguin effects that can resolve to the B--> K pi puzzle. We also point out that a non-universal AA-terms is an essential requirement for this solution.Comment: 9 pages, 2 figure
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