Heavy-to-Light Meson Transitions in QCD

I discuss QCD sum rules determinations of the form factors governing the decay $B \to \pi (\rho) \ell \nu$. For some of these form factors the computed dependence on the momentum transferred does not agree with the expectation from the nearest pole dominance hypothesis. Relations are observed among the form factors, that seem to be compatible with equations recently derived by B.Stech. The measurement of a number of color suppressed nonleptonic B decay rates could shed light on the accuracy of the calculation of these form factors and on the factorization approximation.Comment: LaTex, 7 pages, 2 figures (files included). Talk given at the 6th International Symposium on Heavy Flavours, Pisa, 6-10 June 199

Radiative transitions of DsJ∗(2317)D^*_{sJ}(2317) and DsJ(2460)D_{sJ}(2460)

We study radiative decays of $D^*_{sJ}(2317)$ and $D_{sJ}(2460)$ using light-cone QCD sum rules. In particular, we consider the decay modes $D^*_{sJ}(2317)\to D_s^* \gamma$ and $D_{sJ}(2460)\to D_s^{(*)} \gamma, D^*_{sJ}(2317) \gamma$ and evaluate the hadronic parameters in the transition amplitudes analyzing correlation functions of scalar, pseudoscalar, vector and axial-vector quark currents. In the case of $D^*_{sJ}(2317)\to D_s^* \gamma$ we also consider determinations based on two different correlation functions in HQET. The decay widths turn out to be different than previous estimates obtained by other methods; the results favour the interpretation of $D^*_{sJ}(2317)$ and $D_{sJ}(2460)$ as ordinary $\bar c s$ mesons.Comment: RevTex, 23 pages, 9 eps figure

Electromagnetic form factors of the (rho) meson in light cone QCD sum rules

We investigate the electromagnetic form factors of the (rho) meson in light cone QCD sum rules. We find that the ratio of the magnetic and charge form factors is larger than two at all values of Q^2, (Q^2 >= 0.5 GeV^2). The values of the individual form factors at fixed values of Q^2 predicted by the light cone QCD sum rules are quite different compared to the results of other approaches. These results can be checked in future, when more precise data on (rho) meson form factors is available.Comment: 12 pages, 6 figures, LaTeX formatte

Magnetic Moments of Heavy ΞQ\Xi_{Q} Baryons in Light Cone QCD Sum Rules

The magnetic moments of heavy $\Xi_{Q}$ baryons containing a single charm or bottom quark are calculated in the framework of light cone QCD sum rules method. A comparison of our results with the predictions of the quark models is presented.Comment: 26 Pages, 8 Figures and 1 Tabl

Semileptonic Decay of BB and D→K0∗(1430)ℓˉνD\to K^*_0(1430) \bar{\ell}\nu From QCD Sum Rule

We calculate $B_{(s)}$, and $D_{(s)}$ to $K^*_0(1430)$ transition form factors, and study semileptonic decays of $B_{(s)}$ and $D_{(s)}\to K_0^*(1430) \bar{\ell}\nu$ based on QCD sum rule. Measuring these semileptonic decays with high statistics will give valuable information on the nature of light scalar mesons.Comment: 13 pages, 5 figures,latex,typos and errors correcte

(Pseudo)Scalar Charmonium in Finite Temperature QCD

The hadronic parameters of pseudoscalar ($\eta_c$) and scalar ($\chi_c$) charmonium are determined at finite temperature from Hilbert moment QCD sum rules. These parameters are the hadron mass, leptonic decay constant, total width, and continuum threshold ($s_0$). Results for $s_0(T)$ in both channels indicate that $s_0(T)$ starts approximately constant, and then it decreases monotonically with increasing $T$ until it reaches the QCD threshold, $s_{th} = 4 m_Q^2$, at a critical temperature T = T_c \simeq 180 \; \mbox{MeV} interpreted as the deconfinement temperature. The other hadronic parameters behave qualitatively similarly to those of the $J/\psi$, as determined in this same framework. The hadron mass is essentially constant, the total width is initially independent of T, and after $T/T_c \simeq 0.80$ it begins to increase with increasing $T$ up to $T/T_c \simeq 0.90 \; (0.95)$ for $\chi_c$ ($\eta_c$), and subsequently it decreases sharply up to $T \simeq 0.94 \; (0.99) \; T_c$, for $\chi_c$ ($\eta_c$), beyond which the sum rules are no longer valid. The decay constant of $\chi_c$ at first remains basically flat up to $T \simeq 0.80\; T_c$, then it starts to decrease up to $T \simeq 0.90 \;T_c$, and finally it increases sharply with increasing $T$. In the case of $\eta_c$ the decay constant does not change up to $T \simeq 0.80 \;T_c$ where it begins a gentle increase up to $T \simeq 0.95 \;T_c$ beyond which it increases dramatically with increasing $T$. This behaviour contrasts with that of light-light and heavy-light quark systems, and it suggests the survival of the $\eta_c$ and the $\chi_c$ states beyond the critical temperature, as already found for the $J/\psi$ from similar QCD sum rules. These conclusions are very stable against changes in the critical temperature in the wide range T_c = 180 - 260 \; \mbox{MeV}.Comment: 12 pages, 5 figures. A wide range of critical temperatures has been considered. No qualitative changes to the conclusion

Semileptonic B decays into excited charmed mesons from QCD sum rules

Exclusive semileptonic $B$ decays into excited charmed mesons are studied with QCD sum rules in the leading order of heavy quark effective theory. Two universal Isgur-Wise functions \tau and \zeta for semileptonic B decays into four lowest lying excited $D$ mesons ($D_1$, $D_2^*$, $D'_0$, and $D'_1$) are determined. The decay rates and branching ratios for these processes are calculated.Comment: RevTeX, 17 pages including 2 figure

Pseudoscalar--meson decuplet--baryon coupling constants in light cone QCD

Taking into account the $SU(3)_f$ breaking effects, the strong coupling constants of the $\pi$, $K$ and $\eta$ mesons with decuplet baryons are calculated within light cone QCD sum rules method. It is shown that all coupling constants, even in the case of $SU(3)_f$ breaking, are described in terms of only one universal function. It is shown that for $\Xi^{\ast 0} \to \Xi^{\ast 0} \eta$ transition violation of $SU(3)_f$ symmetry is very large and for other channels when $SU(3)_f$ symmetry is violated, its maximum value constitutes $10$.Comment: 17 Pages, one Figure and 3 Table

Strong decays of DsJ(2317)D_{sJ}(2317) and DsJ(2460)D_{sJ}(2460)

With the identification of ($D_{sJ}(2317), D_{sJ}(2460)$) as the ($0^+$, $1^+$) doublet in the heavy quark effective field theory, we derive the light cone QCD sum rule for the coupling of eta meson with $D_{sJ}(2317) D_s$ and $D_{sJ}(2460) D_s^{*}$. Through $\eta-\pi^0$ mixing we calculate their pionic decay widths, which are consistent with the experimental values (or upper limits). Combining the radiative decay widths derived by Colangelo, Fazio and Ozpineci in the same framework, we conclude that the decay patterns of $D_{sJ}(2317, 2460)$ strongly support their interpretation as ordinary $c \bar s$ mesons.Comment: Comments and suggestions welcome

Semileptonic and Rare BB-meson transitions in a QCD relativistic potential model

Using a QCD relativistic potential model, previously applied to the calculation of the heavy meson leptonic constants, we evaluate the form factors governing the exclusive decays $B\to\rho\ell\nu$, $B\to K^*\gamma$ and $B\to K^*\ell^+\ell^-$. In our approach the heavy meson is described as a $Q\bar q$ bound state, whose wave function is solution of the relativistic Salpeter equation, with an instantaneous potential displaying Coulombic behaviour at small distances and linear behaviour at large distances. The light vector meson is described by using a vector current interpolating field, according to the Vector Meson Dominance assumption. A Pauli-Villars regularized propagator is assumed for the quarks not constituting the heavy meson. Our procedure allows to avoid the description of the light meson in terms of wave function and constituent quarks, and consequently the problem of boosting the light meson wave function. Assuming as an input the experimental results on $B\to K^*\gamma$, we evaluate all the form factors describing the $B\to \rho, K^*$ semileptonic and rare transitions. The overall comparison with the data, whenever available, is satisfactory.Comment: Latex, 19 pages, 3 figure