Related papers: The Rare Decay D^0 -> gamma gamma

Rare $\Lambda_b\to\Lambda l^+l^-$ and $\Lambda_b\to\Lambda\gamma$ decays are investigated in the relativistic quark model based on the quark-diquark picture of baryons. The decay form factors are calculated with the account of all…

We calculate the long distance contribution to $D^{+,0}\to\pi^{+,0}l^+l^-$ decays by the use of a vector meson dominance model, in which the $\phi$-meson plays the central role. The branching ratios obtained are $10^{-6}$ and a few times…

The rare decay b -> s s bar{d} is studied in the supersymmetric standard model by considering the contribution from the chargino box diagrams. We find that this contribution amounts to 10^{-9} in the branching ratio.

A bound on the angle gamma of the unitarity triangle is derived using experimental information on the CP-averaged branching ratios for the rare decays B^+- -> pi^+- K^0 and B^+- -> pi^0 K^+-. The theoretical description is cleaner than the…

A large low-background sample of events (10300) has been collected for the rare decay of kaons in flight K+ -> pi+ e+ e- by experiment E865 at the Brookhaven AGS. The decay products were accepted by a broad band high-resolution charged…

We carry out a detailed study of the branching fractions and lepton pair invariant-mass spectrum of \tau^- ->\pi^- \nu_\tau l^+l^- decays (l=e,\mu). In addition to the model-independent (QED) contributions, we include the…

The first observation of the decay K^+ --> pi^+ gamma gamma is reported. A total of 31 events was observed with an estimated background of 5.1 +- 3.3 events in the pi+ momentum range from 100 MeV/c to 180 MeV/c. The corresponding partial…

V-spin symmetry ($s \leftrightarrow d$ symmetry) forbids the radiative decay $\Xi_{c2}^{0*} \rightarrow \Xi_{c1}^0 \gamma$ in the SU(3) limit. The quark mass term breaks V-spin symmetry and the leading nonanalytic contribution to the…

We study the decay $B_c \rightarrow D_s^* \gamma$. There are two mechanisms contributing to the process. One proceeds through the short distance $b{\rightarrow}s\gamma$ transition and the other occurs through weak annihilation accompanied…

Form factors of rare (B -> K_0*(1430) l^+ l^-$ decay) decay are calculated within three-point QCD sum rules, with (K_0* (1430)) being the p-wave scalar meson. The branching ratios are estimated when only short, as well as short and long…

The contribution of the fourth generation quarks to the rare (B_s -> l^+ l^-) and (B_s -> l^+ l^- gamma) decays are studied. Constraints on the extended Cabibbo-Kobayashi-Maskawa matrix elements |V_{tb} V_{ts}*| and |V_{t'b} V_{t's}*| are…

We calculate the charm quark contribution to the rare decay K+ -> pi+ nu anti-nu in the next-to-next-to-leading order of QCD. This new contribution reduces the theoretical uncertainty in the relevant parameter Pc from +/- 10.1% down to +/-…

The decays $K \to \pi l^{+} l^{-}$, $K \to \pi \gamma \gamma $ and $K \to \pi \nu {\bar \nu}$ are investigated using the higher order terms of the chiral perturbation theory. The counterterms induced by strong, weak and electromagnetic…

Recent disagreement between experimental measurments of CP violating asymmetry in D -> K+ K- and D ->pi+ pi- and theoretical Standard model expectation motivated many studies within the Standard model and beyond. Rare charm decays offer new…

We provide a model-independent framework for the analysis of the radiative B-meson decays B -> K* gamma and B -> rho gamma. In particular, we give a systematic discussion of the various contributions to these exclusive processes based on…

We study the nine possible rare charm meson decays D->Pl^+l^- (P=pi,K,eta,eta') using the Heavy Meson Chiral Lagrangians and find them to be dominated by the long distance contributions. The decay D^+ -> pi^+l^+l^- with the branching ratio…

We show that information on the weak phase gamma can be extracted from the K* pi and rho K decays. Less hadronic uncertainty is involved when the observables of four of these modes are combined together. We further point out two approximate…

We re-estimate the decay branching ratio of $B_s\to 2\gamma$ through $D_s^+D_s^-$ and $D_s^{*+}D_s^{*-}$ intermediate states, in the effective Lagrangian approach. We find that the branching ratio does not exceed a few times $10^{-7}$,…

We re-investigate the radiative charged kaon decay K+- --> pi0 e+- nu_e gamma in chiral perturbation theory, merging the chiral expansion with Low's theorem. We thoroughly analyze the precision of the predicted branching ratio relative to…

The recent Tevatron result on the top quark forward-backward asymmetry, which deviates from its standard model prediction by 3.4$\sigma$, has prompted many authors to build new models to account for this anomaly. Among the various…