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F. De Fazio

Publications and source records attributed to F. De Fazio.

At least 55 records · Page 3Linked to original sources
arXiv2004

The Riddle of Polarization in $B \to VV$ Transitions

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.

hep-ph↗
arXiv2003

Nonfactorizable contributions in B decays to charmonium: the case of $B^- \to K^- h_c$

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 $h_c$.

hep-ph↗
arXiv2003

Understanding $D_{sJ}(2317)$

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.

hep-ph↗
arXiv2003

Coupling $g_{f_0 K^+ K^-}$ and the structure of $f_0(980)$

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.

hep-ph↗
arXiv2002

Massive quark effects in two flavor color superconductors

The high density effective theory formalism (HDET) is employed to describe high density QCD with two massive flavors (2SC). The gap equation is derived and explicitly solved for the gap parameter. The parameters associated to the pseudo Nambu-Goldstone boson of $U(1)_A$ are evaluated in the limit $μ\to\infty$ and $m/μ$ fixed. In particular we find for the velocity of the NG boson the relation $v^2=\sqrt{μ_1^2-m_1^2}\sqrt{μ_2^2-m_2^2}/3μ_1μ_2$.

hep-ph↗
arXiv2002

$B^- \to K^- χ_{c0}$ decay from charmed meson rescattering

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.

hep-ph↗
arXiv2002

On three-body $B^0 \to D^{*-} D^{(*)0} K^+$ decays and couplings of heavy mesons to light pseudoscalar mesons

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 $B^0 \to D^{-} D^{*0} K^+$.

hep-ph↗
arXiv2001

$D_s$ decays to $η$ and $η^\prime$ final states: a phenomenological analysis

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.

hep-ph↗
arXiv2001

Radiative $ϕ$$-$meson decays and $η$-$η^\prime$ mixing: a QCD sum rule analysis

The radiative transitions $ϕ\to ηγ$ and $ϕ\to η^\prime γ$ are analysed using QCD sum-rules. The results we obtain for ${\cal B}(ϕ\to ηγ)=(1.15 \pm 0.2) 10^{-2}$ and ${\cal B}(ϕ\to η^\prime γ)=(1.18 \pm 0.4) 10^{-4}$ are in very good agreement with existing experimental data. The related issue of $η-η^\prime$ mixing is discussed and we give predictions for the $η$ and $η^\prime$ decay constants in the framework of a mixing scheme in the quark-flavour basis.

hep-ph↗
arXiv2001

Probing the structure of $f_0(980)$ through radiative $ϕ$ decays

We consider the radiative transition $ϕ\to f_0 γ$, which is a sensitive probe of the nature of the $f_0(980)$ particle. Using the QCD sum-rule technique, we estimate the branching ratio of such decay mode to be: ${\cal B}(ϕ\to f_0 γ)=(2.7 \pm 1.1) ~ 10^{-4}$, in fair agreement with present experimental data. As for the structure of the $f_0$, the result suggests a sizeable $s {\bar s}$ component; however, this result does not exclude the possibility of further components and allows a more complex structure than indicated by the naive quark model.

hep-ph↗
arXiv2000

B Meson Transitions into Higher Mass Charmed Resonances

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.

hep-ph↗
arXiv1999

B -> X_u l nu decay distributions to order alpha_s

An analytic result for the O(alpha_s corrections to the triple differential B -> X_u l nu decay rate is presented, to leading order in the heavy-quark expansion. This is relevant for computing partially integrated decay distributions with arbitrary cuts on kinematic variables. Several double and single differential distributions are derived, most of which generalize known results. In particular, an analytic result for the O(alpha_s) corrections to the hadronic invariant mass spectrum is presented. The effects of Fermi motion, which are important for the description of decay spectra close to infrared sensitive regions, are included. The behaviour of perturbation theory in the region of time-like momenta is also investigated

hep-ph↗
arXiv1999

Using Heavy Quark Spin Symmetry in Semileptonic $B_c$ Decays

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.

hep-ph↗
arXiv1999

Radiative Leptonic $B_c$ 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.

hep-ph↗
arXiv1999

Analysis of the Three-Body $B \to D^+ D^- π^0$ Decay

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 $B\to D^+ D^- K_S$.

hep-ph↗
arXiv1998

Universal Isgur-Wise form factors from QCD sum rules in HQET

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.

hep-ph↗
arXiv1998

B decays to excited charm mesons

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 $J^P=(0^+_{1/2},1^+_{1/2})$.

hep-ph↗