2,450 research outputs found

    Factorization of Radiative Leptonic Decays of B−B^- and D−D^- Mesons Including the Soft Photon Region

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    In this work, we study the radiative leptonic decays of B−B^- and D−D^- mesons using factorization approach. Factorization is proved to be valid explicitly at 1-loop level at any order of O(ΛQCD/mQ)O(\Lambda_{\rm QCD}\left/m_Q\right.). We consider the contribution in the soft photon region that Eγ∼ΛQCD2/mQE_{\gamma} \sim \left. \Lambda^2_{\rm QCD} /\right. m_Q. The numerical results shows that, the soft photon region is very important for both the BB and DD mesons. The branching ratios of B→γeνeB\to \gamma e\nu_e is 5.21×10−65.21\times 10^{-6}, which is about 33 times of the result obtained by only considering the hard photon region Eγ∼mQE_{\gamma}\sim m_Q. And for the case of D→γeνeD\to \gamma e\nu_e, the result of the branching ratio is 1.92×10−51.92\times 10^{-5}.Comment: arXiv admin note: text overlap with arXiv:1409.035

    Factorization of Radiative Leptonic Decays of B−B^- and D−D^- Mesons

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    In this work, we study the factorization of the radiative leptonic decays of B−B^- and D−D^- mesons, the contributions of the order O(ΛQCD/mQ)O(\Lambda _{\rm QCD}\left/m_Q\right.) are taken into account. The factorization is proved to be valid explicitly at the order O(αsΛQCD/mQ)O(\alpha _s\Lambda _{\rm QCD}\left/m_Q\right.). The hard kernel is obtained. The numerical results are calculated using the wave-function obtained in relativistic potential model. The O(ΛQCD/mQ)O(\Lambda _{\rm QCD}\left/m_Q\right.) contribution is found to be very important, the correction to the decay amplitudes of B−→γeνˉB^-\to \gamma e\bar{\nu} is about 20%−30%20\% - 30\%. For DD mesons, the O(ΛQCD/mQ)O(\Lambda _{\rm QCD}\left/m_Q\right.) contributions are more important.Comment: 26 pages, 8 figures. Version to appear in Nucl. Phys.

    B to light meson transition form factors calculated in perturbative QCD approach

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    We calculate the B→PB\to P, B→VB\to V (P: light pseudoscalar meson, V light vector meson) form factors in the large-recoil limit in perturbative QCD approach, including both the vector (axial vector) and tensor operators. In general there are two leading components ϕB\phi_B and ϕˉB\bar{\phi}_B for BB meson wave functions. We consider both contributions of them. Sudakov effects (k⊥k_{\perp} and threshold resummation) are included to regulate the soft end-point singularity. By choosing the hard scale as the maximum virtualities of internal particles in the hard bb-quark decay amplitudes, Sudakov factors can effectively suppress the long-distance soft contribution. Hard contribution can be dominant in these approaches.Comment: 21 pages, with 2 figure

    Radiative and leptonic decays of the pseudoscalar charmonium state ηc\eta_c

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    The radiative and leptonic decays of ηc→γγ\eta_c\to \gamma\gamma and ηc→l+l−\eta_c\to l^+l^- are studied. For ηc→γγ\eta_c\to \gamma\gamma decay, the second-order electromagnetic tree-level diagram gives the leading contribution. The decay rate of ηc→γγ\eta_c\to \gamma\gamma is calculated, the prediction is in good agreement with the experimental data. For \eta_c\to l^+\l^-, both the tree and loop diagrams are calculated. The analysis shows that the loop contribution dominates, the contribution of tree diagram with Z0Z^0 intermediate state can only modifies the decay rate by less than 1%. The prediction of the branching ratios of ηc→e+e−\eta_c\to e^+e^- and μ+μ−\mu^+\mu^- are very tiny within the standard model. The smallness of these predictions within the standard model makes the leptonic decays of ηc\eta_c sensitive to physics beyond the standard model. Measurement of the leptonic decay may give information of new physics.Comment: 9 pages, 4 figures, RevTex, small change, version to appear in Phys. Rev.

    Spectrum of the charmed and b-flavored mesons in the relativistic potential model

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    We study the bound states of heavy-light quark-antiquark system in the relativistic potential model, where the potential includes the long-distance confinement term, the short-distance Coulomb term and spin-dependent term. The spectrum of BB, B∗B^*, DD, D∗D^* and states with higher orbital quantum numbers are obtained. Compared with previous results predicted in the relativistic potential model, the predictions are improved and extended in this work, more theoretical masses are predicted which can be tested in experiment in the future.Comment: 10 pages, no figure, 2 tables, more discussion is added. Version to appear in JHE
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