arXiv subjects

P. Colangelo

Publications and source records attributed to P. Colangelo.

84 records · Page 5Linked to original sources

arXiv1994

Form Factor $A_0(q^2)$, Non Leptonic $D(B) \to PV$ Transitions and Rare $B \to K^* γ$ Decays

We use three-point function QCD sum rules to calculate the form factor $A_0(q^2)$ appearing in the matrix element of the flavour-changing axial current between the $D (B)$ state and a vector meson state. We describe the role of this form factor in nonleptonic $D (B) \to P V$ decays and analyze the light $SU(3)_F$ symmetry breaking effects. We also discuss a proposal to relate the branching ratio of $B \to K^* γ$ to the spectrum of the semileptonic $B \to ρ\ell ν$ decay.

hep-ph↗

arXiv1994

Couplings of heavy mesons with soft pions in QCD

QCD sum rules are used to calculate the couplings of heavy-light quark pseudoscalar and vector mesons ($D, D^*$ and $B, B^*$) with soft pions, both for finite and infinitely heavy quark mass. The couplings are also computed in the framework of a QCD relativistic potential model; in this approach the relativistic corrections due to the light quark are relevant.

hep-ph↗

arXiv1994

$D^*$ Radiative Decays and Strong Coupling of Heavy Mesons with Soft Pions in a QCD Relativistic Potential Model

In the framework of a QCD inspired relativistic potential model, we evaluate radiative decay rates of heavy mesons and their coupling with soft pions. The agreement with the existing experimental data is satisfactory. In the limit $m_Q \to \infty$ one obtains results in agreement with the Heavy Quark Effective Theory and is able to predict the values of the relevant couplings; in particular, for the scaled $B^*B π$ strong coupling constant $g$, we find that the non relativistic constituent quark model prediction $g=1$ is modified, by the inclusion of the relativistic effects due to the light quarks, to the value $g=1/3$, in agreement with recent QCD sum rules determination.

hep-ph↗

arXiv1994

On the coupling of heavy mesons to pions in QCD

We compute the strong coupling constant $g_{P^* P π}$, with $P$ and $P^*$ respectively pseudoscalar and vector heavy mesons by using the QCD sum rules approach. Our computation is based on the evaluation of the time ordered product of currents between the vacuum and the soft pion state. The so-called parasitic terms are taken into account and give a contribution to the sum rule of the same order of the lowest lying state, while higher dimension non perturbative terms have small numerical effects. The infinite heavy quark mass limit is also examined.

hep-ph↗

arXiv1994

Higgs Search by Neural Networks at LHC

We show that neural network classifiers can be used to discriminate Higgs production from background at LHC for $ 150< M_H<200$ GeV. The results compare favourably with ordinary multivariate analysis.

hep-ph↗

arXiv1993

Dependence of the Form Factors of $B \to π\ell ν$ on the Heavy Quark Mass

We use QCD sum rules to analyze the semileptonic transition $B \to π\ell ν$ in the limit $m_b \to \infty$. We derive the dependence of the form factor $F_1(0)$ on the heavy quark mass, which is compatible with the expected dependence for the simple pole model of $F_1(q^2)$.

hep-ph↗

arXiv1993

QCD Calculation of Heavy Meson Semileptonic Transitions

I review the QCD sum rules calculations of the form factors governing the semileptonic decays of charmed and beauty mesons. In particular, I discuss the predicted dependence of the various form factors on $q^2$ and how it can be obtained for the form factors of vector and axial currents. In some cases the $q^2$ dependence, computed by QCD sum rules, is different from the outcome of lattice QCD. A Tau-Charm factory could be an efficient tool to study this aspect of the charmed meson transitions.

hep-ph↗

arXiv1993

Radiative $B \to K^* γ$ transition in QCD

We evaluate the branching ratios of the radiative decays $B \to K^* γ$, and $B \to K_1 γ$ in the framework of three-point function QCD sum rules. We find: $ Γ(B \to K^* γ) / Γ(b \to s γ) = 0.17 \pm 0.05$ and $ Γ(B \to K_1 γ) / Γ(b \to s γ) = 0.30 \pm 0.15$. We also study, in the infinite quark mass limit, the connection between the form factor of the radiative $B \to K^* γ$ transition and the weak hadronic form factors entering the semileptonic B-meson decays.

hep-ph↗

arXiv1993

Radiative Heavy Meson Transitions

We evaluate the radiative and hadronic decay rates of the $D^*$ mesons using the Heavy Quark Effective Theory and the Vector Meson Dominance hypothesis. We also estimate the width of the $B^*$ electromagnetic transitions and the radiative decays of positive parity $J^P=0^+, 1^+$ charmed mesons.

hep-ph↗

arXiv1993

Phenomenology of $B_s$ Decays

Using the QCD sum rules technique we study several aspects of the phenomenology of the b-flavoured strange meson $B_s^0$. In particular, we evaluate the mass of the particle, the leptonic constant and the form factors of the decays $\overline {B_s^0} \to D^{+}_s \ell^- \barν$, $\overline {B_s^0} \to D^{*+}_s \ell^- \barν$, $\overline {B_s^0} \to K^{*+} \ell^- \barν$. We also calculate, in the factorization approximation, a number of two-body non leptonic $\overline {B_s^0}$ decays.

hep-ph↗

arXiv1993

QCD Sum Rules and B Decays

We review some recent applications of QCD sum rules to $B$-decays. These include the determination of the leptonic constant $f_B$ and of the semileptonic transition amplitudes of the $B$-meson into negative and positive parity charmed states.

hep-ph↗

arXiv1993

Study of the Reactions $B \to D^* ππ$ and $B \to D^* ρπ$

We evaluate the non leptonic decays $B \to D^* ππ$ and $B \to D^* ρπ$ in the limit of infinitely heavy quarks, assuming the dominance of intermediate positive parity charmed resonances. We find that the branching ratios are of the order $10^(-3)$.

hep-ph↗