365 research outputs found

    Effects of Littlest Higgs model in rare D meson decays

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    A tree-level flavor changing neutral current in the up-like quark sector appears in one of the variations of the Littlest Higgs model. We investigate the effects of this coupling in the D+ -> pi+ l+ l- and D0 -> rho0 l+ l- decays, which are the most appropriate candidates for the experimental studies. However, the effects are found to be too small to be observed in the current and the foreseen experimental facilities. These decays are still dominated by the standard model long-distance contributions, which are reevaluated based on the new experimental input.Comment: 13 pages, 3 figures; new constraint on scale f taken into account and effects on charm meson decays recalculate

    Rare Charm Decays

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    Rare FCNC decay modes of charmed mesons are reviewed. The standard model predictions, including both short and long distance contributions, are summarized. Several new physics options that can give detectable signals are described.Comment: 4 pages. Presented at the 6th International Conference on Hyperons, Charm and Beauty Hadrons, IIT, Chicago, june 27-july 3, 2004. To be published in the Proceeding

    Long distance contribution to BKKπ+B^- \to K^- K^- \pi^+, - a searching ground mode for new physics

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    The decay BKKπ+B^- \to K^- K^- \pi^+ has been sugested as a test for minimal supersymmetric standard model and for supersymmetric models with R-parity violating couplings, in view of its extreme smallnesss in the standard model. We calculate two long distance contributions to this decay, that associated with DDDD and DπD\pi intermediate states and that induced by virtual DD, π\pi mesons. The branching ratio due to these contributions is 6×10126 \times 10^{-12}, which is somewhat smaller than the standard model short distance result, leaving this decay free for the search of new physics.Comment: 13 pages, 2 figures, revised versio

    A Possible Arena for Searching New Physics - the Γ(D0ρ0γ)/Γ(D0ωγ)\Gamma(D^0 \to \rho^0 \gamma)/\Gamma (D^0 \to \omega \gamma) Ratio

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    We propose to investigate flavour changing neutral currents in the cuγc \to u \gamma transition through the measurement of the difference between Γ(D0ρ0γ)\Gamma (D^0 \to \rho^0 \gamma) and Γ(D0ωγ)\Gamma (D^0 \to \omega \gamma). This is based on the observation that D0(ddˉ)γD^0 \to (d \bar d) \gamma is due to long distance physics while D0(uuˉ)γD^0 \to (u \bar u) \gamma arises from the cuγc \to u \gamma transition. The effect of ρω\rho - \omega mixing is included. A difference in the decay widths of more than about 30% would be indicative of new physics.Comment: 7 pages, 1 figure include

    Updated constraints on new physics in rare charm decays

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    Motivated by recent experimental results on charm physics we investigate implications of the updated constraints of new physics in rare charm meson decays. We first reconsider effects of the MSSM in cuγc\to u \gamma constrained by the recent experimental evidence on ΔmD\Delta m_D and find, that due to the dominance of long distance physics, DVγD \to V \gamma decay rates cannot be modified by MSSM contributions. Then we consider effects of the extra heavy up vector-like quark models on the decay spectrum of D+π+l+lD^+ \to \pi^+ l^+ l^- and Ds+K+l+lD_s^+ \to K^+ l^+ l^- decays. We find a possibility for the tiny increase of the differential decay rate in the region of large dilepton mass. The R-parity violating supersymmetric model can also modify short distance dynamics in cul+lc \to u l^+ l^- decays. We constrain relevant parameters using current upper bound on the D+π+l+lD^+ \to \pi^+ l^+ l^- decay rate and investigate impact of that constraint on the Ds+K+l+lD_s^+ \to K^+ l^+ l^- differential decay dilepton distribution. Present bounds still allow small modification of the standard model differential decay rate distribution.Comment: 15 pages, 4 figure

    Long distance contributions in DVγD \to V \gamma decays

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    Using the factorization scheme for the nonleptonic DVV0D \to V V_0 weak amplitudes, we classify all diagrams which arise in DVγD \to V \gamma decays and calculate them with the help of the hybrid model which combines the heavy quark effective theory and the chiral Lagrangian approach. Thus we determine the long distance contribution to the amplitudes of Cabibbo allowed and Cabibbo suppressed DVγD \to V\gamma decays. The calculation of the expected range of the branching ratios of nine different DVγD \to V \gamma channels is compared with results of other approaches. The present work establishes an increase of the parity violating contribution in these decays in comparison with previous analyses.Comment: 15 pages, latex, 2 figures; we have changed Table 2 and the caption of Table 1. To be published in Eur. Phys.