Analysis of the semileptonic (B_c -> B_u* l+ l-) decay from QCD sum rules

We analyze the semileptonic (B_c -> B_u* l+ l-) decay in the frame work of the Standard Model. We calculate the (B_c) to (B_u*) transition form factors in QCD sum rules. Analytical expressions for the spectral densities and gluon condensates are presented. The branching ratio of the (B_c -> B_u* l+ l-) decay is calculated, and it is obtained that this decay can be detectable at forthcoming LHC machines.Comment: 17 pages, no figures, LaTeX formatte

D−DˉD-\bar{D} mixing constraints on FCNC with a non-universal Z′Z^\prime

The BaBar and Belle collaborations have recently reported evidence for $D^0-\bar D^0$ mixing. This measurement provides the first significant constraint on FCNC in the up-quark sector for non-universal $Z^\prime$ models. Attributing the observed $D-\bar D$ mixing to new physics, we comment on the resulting rare $D$ and $t$ decays. We also show that a CP violating semileptonic asymmetry as large as $\sim 30$ is allowed by the experimental results.Comment: RevTex, 10 pages, 1 figure. Several typoes correcte

Mixing and CP-violation in charm

The motivation most often cited in searches for D0-anti-D0 mixing and CP-violation in charm system lies with the possibility of observing a signal from new physics which dominates that from the Standard Model. We review recent theoretical predictions and experimental constraints on D0-anti-D0 mixing parameters. We also discuss the current status of searches for CP-violation in charmed meson transitions, as well as some recent theoretical ideas.Comment: 7 pages, 1 figure, 1 table, invited talk at BEACH 2004, 6th international conference on Hyperons, Charm and Beauty Hadrons, Illionois Institute of Technology, Chicago, June 27 - July 3, 200

D^0 - D^0-bar Oscillations as a Probe of Quark-Hadron Duality

It is usually argued that the Standard Model predicts slow D^0-\bar D^0 oscillations with \Delta M_D, \Delta \Gamma_D < 10^{-3}*\Gamma_D$ and that New Physics can reveal itself through \Delta M_D exceeding 10^{-3}*\Gamma_D. It is believed that the bulk of the effect is due to long distance dynamics that cannot be described at the quark level. We point out that in general the OPE yields soft GIM suppression scaling only like (m_s/\mu_{hadr})^2 and even like m_s/\mu_{hadr} rather than m_s^4/m_c^4 of the simple quark box diagram. Such contributions can actually yield \Delta M_D, \Delta \Gamma_D \sim O(10^{-3})*\Gamma_D without invoking additional long distance effects. They are reasonably suppressed as long as the OPE and local duality are qualitatively applicable in the 1/m_c expansion. We stress the importance of improving the sensitivity on \Delta \Gamma_D as well as \Delta M_D in a dedicated fashion as a laboratory for analyzing the onset of quark-hadron duality and comment on the recent preliminary study on \Delta \Gamma_D by the FOCUS group.Comment: 15 pages, LaTeX. Revised: A reference and a few clarifications in the text are added. A few inconsistencies in equations are eliminated. We found the standard contribution to Delta M_D to differ from the expression usually quoted in the literatur

Charm Physics 1996 - A Retrospective

A pedagogically oriented review is given of progress made over the past year in our understanding of physics related to the charm quark. Included are discussions of the R_c deficit, the \psi' anomaly, charm spectroscopy, D nonleptonic decays, searches for flavor-changing neutral currents, new limits on D^0 - {\bar D}^0 mixing and prospects for future experimental studies of the charm sector.Comment: 11 pages, LaTeX, 5 figures, 7 tables. Invited talk at Fourth KEK Topical Conference on Flavor Physics, 29-31 October 1996. To be published in Nucl. Phys. B (Proc. Suppl.

Impact of colored scalars on D0−Dˉ0D^0-\bar D^0 mixing in diquark models

Inspired by the recent observation of the $D^0-\bar D^0$ mixing, we explore the effects of colored scalars on the $\Delta C=2$ process in diquark models. As an illustration, we investigate the diquarks with the quantum numbers of (6, 1, 1/3) and (6, 1, 4/3) under $SU(3)_C\times SU(2)_L\times U(1)_Y$ gauge symmetries, which contribute to the process at one-loop and tree levels, respectively. We show that $\Delta m_D$ gives the strongest constraint on the free parameters. In addition, we find that the small couplings can be naturally interpreted by the suppressed flavor mixings if the diquark of (6, 1, 4/3) only couples to the third generation.Comment: 11 pages, 3 figures, references added, final version to appear PL

CP-Violating Observables in Tagged D0D^0--Dˉ0\bar{D}^0 Decays

We perform a systematic study of CP-violating observables in \ddbar\ decays. We show that given a final state, which may be a CP eigenstate or not, all the observables can in principle be measured if decay-time information is available and if, for CP non-eigenstates, both decay rates into $f$ and $\bar f$ are considered. As an illustration of our analysis we discuss an effective superweak scenario.Comment: 9 pages LATEX, no figure

Calculation of Long-Distance Effects in Exclusive Weak Radiative Decays of B-Mesons

We calculate the contribution of the weak annihilation to the $B\rightarrow \rho\gamma$ decay amplitude by means of QCD sum rules using the photon light-cone wave function. We find that this long-distance contribution amounts to about 10\% of the leading short-distance effect in $B^-\rightarrow \rho^-\gamma$. On the other hand, weak annihilation is the dominant source of the corresponding $D$ meson decays and according to our estimates, yields branching ratios of $O(10^{-4})$ for $D^0\rightarrow \bar{K}^{*0}\gamma$, $O(10^{-5})$ for $D_s\rightarrow \rho^+\gamma$, and $O(10^{-6})$ for $D^-\rightarrow \rho^-\gamma$ and for $D^0\rightarrow \rho^0\gamma$.Comment: 14 pages, Latex, two figures added as an uuencoded .ps fil

Rare Charm Decays in the Standard Model and Beyond

We perform a comprehensive study of a number of rare charm decays, incorporating the first evaluation of the QCD corrections to the short distance contributions, as well as examining the long range effects. For processes mediated by the $c\to u\ell^+\ell^-$ transitions, we show that sensitivity to short distance physics exists in kinematic regions away from the vector meson resonances that dominate the total rate. In particular, we find that $D\to\pi\ell^+\ell^-$ and $D\to\rho\ell^+\ell^-$ are sensitive to non-universal soft-breaking effects in the Minimal Supersymmetric Standard Model with R-parity conservation. We separately study the sensitivity of these modes to R-parity violating effects and derive new bounds on R-parity violating couplings. We also obtain predictions for these decays within extensions of the Standard Model, including extensions of the Higgs, gauge and fermion sectors, as well as models of dynamical electroweak symmetry breaking.Comment: 45 pages, typos fixed, discussions adde

Weak Radiative Decays of Beauty Baryons

Weak radiative decays of beauty baryons into strange baryons, induced by the electroweak penguin, are estimated by using a quark model approach. Relations between formfactors in the semileptonic and in the weak radiative decays are derived within the heavy quark effective theory. The partial decay widths are found to be of the order of $10^{-15}{\rm MeV}$ for $\Lambda_b\rightarrow\Lambda\gamma$ and $\Xi_b\rightarrow\Xi\gamma$ and of the oder of $10^{-13}{\rm MeV}$ for $\Omega_b\rightarrow\Omega\gamma$. The $\Omega_b$ radiative decay is thus expected at the sizable branching ratio of approximately $10^{-4}$.Comment: 10 pages, latex, no figure