19,836,333 research outputs found

    Color suppressed contributions to the decay modes B_{d,s} -> D_{s,d} D_{s,d}, B_{d,s} -> D_{s,d} D^*_{s,d}, and B_{d,s} -> D^*_{s,d} D^*_{s,d}

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    The amplitudes for decays of the type Bd,sDs,dDs,dB_{d,s} \to D_{s,d} D_{s,d}, have no factorizable contributions, while Bd,sDs,dDs,dB_{d,s} \to D_{s,d} D^*_{s,d}, and Bd,sDs,dDs,dB_{d,s} \to D^*_{s,d} D^*_{s,d} have relatively small factorizable contributions through the annihilation mechanism. The dominant contributions to the decay amplitudes arise from chiral loop contributions and tree level amplitudes which can be obtained in terms of soft gluon emissions forming a gluon condensate. We predict that the branching ratios for the processes Bˉd0Ds+Ds\bar B^0_d \to D_s^+ D_s^-, Bˉd0Ds+Ds\bar B^0_d \to D_s^{+*} D_s^- and Bˉd0Ds+Ds\bar B^0_d \to D_s^+ D_s^{-*} are all of order (23)×104(2- 3) \times 10^{-4}, while Bˉs0Dd+Dd\bar B^0_s \to D_d^+ D_d^-, Bˉs0Dd+Dd\bar B^0_s \to D_d^{+*} D_d^- and Bˉs0Dd+Dd\bar B^0_s \to D_d^+ D_d^{-*} are of order (47)×103(4- 7) \times 10^{-3}. We obtain branching ratios for two DD^*'s in the final state of order two times bigger.Comment: 15 pages, 4 figure

    Riesz s-Equilibrium Measures on d-Dimensional Fractal Sets as s Approaches d

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    Let AA be a compact set in \Rp of Hausdorff dimension dd. For s(0,d)s\in(0,d), the Riesz ss-equilibrium measure μs,A\mu^{s,A} is the unique Borel probability measure with support in AA that minimizes \Is(\mu):=\iint\Rk{x}{y}{s}d\mu(y)d\mu(x) over all such probability measures. In this paper we show that if AA is a strictly self-similar dd-fractal, then μs,A\mu^{s,A} converges in the weak-star topology to normalized dd-dimensional Hausdorff measure restricted to AA as ss approaches dd from below

    Measurement of the D-s+-D-s- production asymmetry in 7 TeV pp collisions

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    Heavy quark production in 7 TeV centre-of-mass energy pp collisions at the LHC is not necessarily flavour symmetric. The production asymmetry, AP, between and mesons is studied using the ϕπ± decay mode in a data sample of 1.0 fb−1 collected with the LHCb detector. The difference between π+ and π− detection efficiencies is determined using the ratios of fully reconstructed to partially reconstructed D⁎± decays. The overall production asymmetry in the rapidity region 2.0 to 4.5 with transverse momentum larger than 2 GeV is measured to be AP=(−0.33±0.22±0.10)%. This result can constrain models of heavy flavour production

    Measurements of the branching fractions of the decays B°s → D∓s K± and B°s → D¯sπ+

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    The decay mode B°s → D∓s K± allows for one of the theoretically cleanest measurements of the CKM angle γ through the study of time-dependent CP violation. This paper reports a measurement of its branching fraction relative to the Cabibbo-favoured mode B°s → D¯sπ+ based on a data sample corresponding to 0.37 fb¯¹ of proton-proton collisions at √s = 7TeV collected in 2011 with the LHCb detector. In addition, the ratio of B meson production fractions fs/fd, determined from semileptonic decays, together with the known branching fraction of the control channel B°s → D¯sπ+ is used to perform an absolute measurement of the branching fractions: B(B°s → D¯sπ+) = (2.95 ± 0.05 ± 0.17 -0.22 +0.18) × 10¯³ ; B(B°s → D∓s K±) = (1.90 ± 0.12 ± 0.13 -0.14 +0.12) × 10¯4 ; where the first uncertainty is statistical, the second the experimental systematic uncertainty, and the third the uncertainty due to f s/f

    Constraints on charged Higgs bosons from D(s)+- -> mu+- nu and D(s)+- -> tau+- nu

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    The decays D(s)+- -> mu+- nu and D(s)+- -> tau+- nu have traditionally been used to measure the D(s)+- meson decay constant f_D(s). Recent measurements at CLEO-c and the B factories suggest a branching ratio for both decays somewhat higher than the Standard Model prediction using f_D(s) from unquenched lattice calculations. The charged Higgs boson (H+-) in the Two Higgs Doublet Model (Type II) would also mediate these decays, but any sizeable contribution from H+- can only suppress the branching ratios and consequently is now slightly disfavoured. It is shown that constraints on the parameters tan(beta) and m_H+- from such decays can be competitive with and complementary to analogous constraints derived from the leptonic meson decays B+- -> tau+- nu_tau and K+- -> mu+- nu_mu, especially if lattice calculations eventually prefer f_D(s) < 250 MeV.Comment: 18 pages, 4 figure
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