arXiv subjects
Publications and source records attributed to P. Colangelo.
We use recent experimental data on charmed mesons to constrain three coupling constants in the effective lagrangian describing the interactions of excited heavy-light mesons with light pseudoscalar mesons at order $m_Q^{-1}$. Predictions in the beauty sector are also derived.
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 $D^*_{sJ}(2317)\to D_s^* γ$ and $D_{sJ}(2460)\to D_s^{(*)} γ, D^*_{sJ}(2317) γ$ 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 $D^*_{sJ}(2317)\to D_s^* γ$ 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.
We review the status of recently observed positive parity charmed resonances, both in the non-strange and in the strange sector. We describe the experimental findings, the main theoretical analyses and the open problems deserving further investigations.
Measurements of polarization fractions in $B \to VV$ transitions, with $V$ a light vector meson, show that the longitudinal amplitude dominates in $B^0 \to ρ^+ ρ^-$, $B^+ \to ρ^+ ρ^0$, and $B^+ \to ρ^0 K^{*+}$ decays and not in the penguin induced decays $B^0 \to ϕK^{*0}$, $B^+ \to ϕK^{*+}$. We study the effect of rescattering mediated by charmed resonances, finding that in $B \to ϕK^*$ it can be responsible of the suppression of the longitudinal amplitude. For the decay $B \to ρK^*$ we find that the longitudinal fraction cannot be too large without invoking new effects.
Nonleptonic $B$ to charmonium decays generally show deviations from the factorization predictions. For example, the mode $B^- \to K^- χ_{c0}$ has been experimentally observed with sizeable branching fraction while its factorized amplitude vanishes. We investigate the role of rescattering effects mediated by intermediate charmed meson production in this class of decay modes, and consider $B^- \to K^- h_c$ with $h_c$ the $J^{PC}=1^{+-}$ $\bar c c$ meson. Using an effective lagrangian describing interactions of pairs of heavy-light $Q{\bar q}$ mesons with a quarkonium state, we relate this mode to the analogous mode with $χ_{c0}$ in the final state. We find ${\cal B}(B^- \to K^- h_c)$ large enough to be measured at the $B$ factories, so that this decay mode could be used to study the poorly known $h_c$.
We analyze the hadronic and radiative decay modes of the recently observed $D_{sJ}(2317)$ meson, in the hypothesis that it can be identifield with the scalar $s_\ell^P={1\over 2}^+$ state of $c \bar s$ spectrum ($D_{s0}$). The method is based on heavy quark symmetries and Vector Meson Dominance ansatz. We find that the hadronic isospin violating mode $D_{s0} \to D_s π^0$ is enhanced with respect to the radiative mode $D_{s0} \to D_s^* γ$. The estimated width of the meson is $Γ(D_{s0})\simeq 7$ KeV.
We use light-cone QCD sum rules to evaluate the strong coupling $g_{f_0 K^+ K^-}$ which enters in several analyses concerning the scalar $f_0(980)$ meson. The result: $6.2\le g_{f_0 K^+ K^-}\le 7.8$ GeV is larger than in previous determinations.
I briefly describe the use of the three-body decay modes $B^0 \to D^{(*)-} D^{(*)0} K^+$ to investigate open issues in charmed meson spectroscopy, and of the time dependent $B^0 (\bar {B^0}) (t) \to D^{-} D^{+} π^0$ transitions for a measurement of $\cos (2 β)$.
We study the process $B^- \to K^- χ_{c0}$ considering intermediate charmed meson rescattering effects. For this decay mode the naive factorization ansatz would predict a vanishing amplitude. We estimate contributions from the $D^{(*)}_{s} D^{(*)}\to K^- χ_{c0}$ rescattering amplitudes, and compare the result with recent experimental measurements. We find that rescattering effects are able to produce a large branching ratio consistent with measurements by Belle Collaboration. We also consider rescattering effects in $B^- \to K^- J/ψ$, arguing that they play a similar role in producing a large branching fraction for this colour-suppressed decay mode.
We analyze the decay modes $B^0 \to D^{*-} D^0 K^+$ and $B^0 \to D^{*-} D^{*0} K^+$ and, using the available experimental data, we find bounds for the constants g and h describing the strong coupling of heavy mesons to light pseudoscalar mesons. Both the decay channels are dominated by broad L=1 charm resonances; the dominance is effective also in $B^0 \to D^{-} D^0 K^+$ and $B^0 \to D^{-} D^{*0} K^+$.
We consider the semileptonic and nonleptonic $D_s$ decay modes to final states with $η$ and $η^\prime$. We use QCD sum rules to determine the $D_s \to η$ form factor $f_+^η$, and a generalized factorization ansatz to compute nonleptonic decays. We propose a parameterization of possible OZI suppressed contributions producing the $η^\prime$ in the final state, compatible with current data; such a scheme can be further constrained improving the precision of the measurement of the $D_s$ decay rates, as expected by the ongoing experiments.
We use QCD sum rules to estimate the universal form factors describing the semileptonic B decays into excited charmed resonances, such as the $1^-$ and $2^-$ states $D_1^{*}$ and $D_2^{*}$ belonging to the $s_\ell^P={3/2}^-$ heavy quark doublet, and the $2^-$ and $3^-$ states $D_2^{*\prime}$ and $D_3$ belonging to the $s_\ell^P={5\2}^-$ doublet.
The form factors parameterizing the B_c semileptonic matrix elements can be related to a few invariant functions if the decoupling of the spin of the heavy quarks in B_c and in the mesons produced in the semileptonic decays is exploited. We compute the form factors as overlap integral of the meson wave-functions obtained using a QCD relativistic potential model, and give predictions for semileptonic and non-leptonic B_c decay modes. We also discuss possible experimental tests of the heavy quark spin symmetry in B_c decays.
We analyze the radiative leptonic $B_c$ decay mode: $B_c \to \ell νγ$ ($\ell=e, μ$) using a QCD-inspired constituent quark model. The prediction: ${\cal B}(B_c \to \ell νγ)\simeq 3 \times 10^{-5}$ makes this channel experimentally promising in view of the large number of $B_c$ mesons which are expected to be produced at the future hadron facilities.
The decay process $B\to D^+ D^- π^0$ is an interesting channel for the investigation of CP violating effects in the $b-$ sector. We write down a decay amplitude constrained by a low-energy theorem, which also includes the contribution of resonant $S-$ and $P-$wave beauty and charmed mesons, and we determine the relevant matrix elements in the infinite heavy quark mass limit, assuming the factorization ansatz. We estimate the rate of the decay: ${\cal B}(B \to D^+ D^- π^0)\simeq 1 \times 10^{-3}$. We also analyze the time-independent and time-dependent differential decay distributions, concluding that a signal for this process should be observed at the B-factories. Finally, we give an estimate of the decay rate of the Cabibbo-favoured process $B\to D^+ D^- K_S$.
We review the role of the universal Isgur-Wise functions parameterizing the $B$ meson semileptonic matrix elements to charm states in the infinite heavy quark mass limit. We also discuss the determination of one of such form factors by QCD sum rules in the framework of the Heavy Quark Effective Theory.
We review several aspects of the phenomenology of P-wave $\bar q Q$ mesons: mass splittings, effective strong couplings and leptonic constants. We also describe a QCD sum rule determination to order $α_s$ of the form factor $τ_{1/2}(y)$ governing the semileptonic $B$ decays to the charm doublet with $J^P=(0^+_{1/2},1^+_{1/2})$.