555 research outputs found

    Pure Leptonic Radiative Decays B±,DsνγB^\pm, D_s\to\ell\nu\gamma and the Annihilation Graph

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    Pure leptonic radiative decays of heavy-light mesons are calculated using a very simple non-relativistic model. Dominant contribution originates from photon emission from light initial quark. We find BR(B±νγ)3.5×106BR(B^\pm\to\ell\nu\gamma)\sim3.5\times10^{-6} and BR(Dsνγ)1.7×104BR(D_s\to \ell\nu\gamma)\sim1.7 \times10^{-4}. The importance of these reactions to clarify the dynamics of the annihilation graph is emphasized.Comment: 7 pages, LaTeX, 3 figure

    Studying the scale and q^2 dependence of K^+-->pi^+e^+e^- decay

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    We extract the K^+-->pi^+e^+e^- amplitude scale at q^2=0 from the recent Brookhaven E865 high-statistics data. We find that the q^2=0 scale is fitted in excellent agreement with the theoretical long-distance amplitude. Lastly, we find that the observed q^2 shape is explained by the combined effect of the pion and kaon form-factor vector-meson-dominance rho, omega and phi poles, and a charged pion loop coupled to a virtual photon-->e^+e^- transition.Comment: 8 pages, 3 figure

    Transverse Tau Polarization in Decays of the Top and Bottom Quarks in the Weinberg Model of CP Non-conservation

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    We show that the transverse polarization asymmetry of the τ\tau-lepton in the decay tbτνt\rightarrow b \tau \nu is extremely sensitive to CP violating phases arising from the charged Higgs exchange in the Weinberg model of CP non-conservation. Qualitatively, the polarization asymmetries are enhanced over rate or energy asymmetries by a factor of mtmτO(100)\approx {m_t\over m_\tau}\approx O(100). Thus for optimal values of the parameters the method requires 104\approx 10^4 top pairs to be observable rather than 10710^7 needed for rate or energy asymmetries. We also examine τ\tau polarization in b decays via bcντb \rightarrow c \nu \tau and find that it can also be very effective in constraining the CP violation parameters of the extended Higgs sector.Comment: 11,1 figure, SLAC-PUB-608

    On the Possibility of a New Boson X^0 (214 MeV) in Sigma^+ -> p mu^+ mu^-

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    We consider the existence of the state X^0 (214 MeV) in Sigma^+ -> p mu^+ mu^- decay found by the HyperCP collaboration. We assume that a fundamental spin zero boson X^0 coupled to quarks leads to flavor changing s -> d X^0 process. We estimate the scalar and pseudoscalar coupling constants by considering Sigma^+ -> p X^0 and K^+ -> pi^+ X^0 processes, and find that pseudoscalar coupling dominates. We then evaluate the branching ratios for K_L -> pi^0 pi^0 X^0, pi^+ pi^- X^0 and Omega^- -> Xi^- X^0 decays. All these rates are found to be in the measurable ranges. We also comment on X^0 coupling to muons and constraints from muon g-2.Comment: 6 pages; typos corrected, references added, 7 page

    Asymmetry in the decay ΩΞγ\Omega^-\to\Xi^-\gamma

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    We consider the asymmetry in the decay ΩΞγ\Omega^-\rightarrow\Xi^-\gamma assuming that a Vector Meson Dominance approach for the sdγs\rightarrow d\gamma transition gives the dominant contribution. Since in this long-distance approximation the decay is due to a single quark transition sdγs\rightarrow d\gamma, the angular distribution asymmetry is given by the single positive asymmetry parameter αh=Ms2Md2Ms2+Md2=0.4±0.1\alpha_h = \frac{M^2_s-M^2_d}{M^2_s+M^2_d} = 0.4\pm0.1. We also discuss the asymmetry in ΞΣγ\Xi \rightarrow \Sigma^-\gamma, which is expected to be between -0.2 and 0.3.Comment: 16 pages,no figures,Late