Paul Singer

KL →μ+μ−, top mass and bottom lifetime

Abstract We study a class of diagrams, that has previously been overlooked, contributing to the (dispersive) electromagnetic part of the K L → μ + μ − amplitude. The strength of this extra contribution can be estimated in different models and could be measured in related processes. By combining these results with those coming from the K 0  K 0 transition (evaluated in the Kobayashi-Maskawa scheme) we obtain rather strong constraints on the t quark mass and the B meson lifetime. The recently measured value for the B meson lifetime is difficult to accommodate unless the t quark is very heavy; m t > 100 GeV could be natural values according to the analysis.

The radiative leptonic decays

Abstract. We present a calculation of the rare decay modes

D^0 \to e^+ e^-\gamma,\mu^+\mu^-\gamma

D^0 \to e^+ e^- \gamma

in the standard model and beyond

and

Long distance contributions in

D^0 \to \mu^+\mu^- \gamma

The ω− → ξ−γ as a measure of the single quark s → dγ transition

in the framework of the standard model. For the short distance part we have derived QCD corrections to the Wilson coefficients involved, including C9. The latter is found to be strongly suppressed by the corrections, leading to diminished values for the

Long distance c ---> u gamma effects in weak radiative decays of D mesons

c\to u l^+l^-

Long-distance contribution to s-->d gamma and implications for Omega ---> Xi - gamma, Bs-->Bd* gamma, and b-->s gamma.

branching ratios in the 10-10 range. Within SM the exclusive decays are dominated by long distance effects. Non-resonant contributions are estimated using heavy quark and chiral symmetries to be at the level of

Resonant and nonresonant contributions to the weak D → Vl + l − decays

10\%

A possible arena for searching new physics – the Γ(D0→ρ0γ)/Γ(D0→ωγ) ratio

, compared to the contributions arising from