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P. Colangelo

Publications and source records attributed to P. Colangelo.

At least 37 records · Page 2Linked to original sources
arXiv2012

Anomalous $AV^*V$ vertex function in the soft-wall holographic model of QCD

We consider the vertex function of two vector and one axial-vector currents using the soft-wall holographic model of QCD with the Chern-Simons term. Two structure functions $w_L$ and $w_T$ describe such a vertex in the special case in which one of the two vector currents corresponds to an on-shell soft photon. We briefly review the QCD results for these functions, obtained from triangular loop diagrams with quarks having mass $m_q=0$ or $m_q \neq 0$, we compute $w_L$ and $w_T$ in the soft-wall model and compare the outcome to the QCD findings. We also calculate and discuss the two-point $Π_{VV}-Π_{AA}$ correlation function, together with a few low-energy constants, which turn out to be close to the QCD results.

hep-ph↗
arXiv2009

Holographic Approach to Finite Temperature QCD: The Case of Scalar Glueballs and Scalar Mesons

We study scalar glueballs and scalar mesons at $T \neq 0$ in the soft wall holographic QCD model. We find that, using the Anti-de Sitter-Black Hole metric for all values of the temperature, the masses of the hadronic states decrease and the widths become broader when T increases, and there are temperatures for which the states disappear from the scalar glueball and scalar meson spectral functions. However, the values of the temperatures in correspondence of which such phenomena occur are low, of the order of 40-60 MeV. A consistent holographic description of in-medium effects on hadron properties should include the Hawking-Page transition, which separates the phase with the Anti-de Sitter metric at small temperatures from the phase with Anti-de Sitter-Black Hole metric at high temperatures.

hep-ph↗
arXiv2009

Investigating AdS/QCD duality through scalar glueball correlators

We investigate AdS/QCD duality for the two-point correlation function of the lowest dimension scalar glueball operator, in the case of the IR soft wall model. We point out the role of the boundary conditions for the bulk-to-boundary propagator in determining the gluon condensates. We show that a low energy QCD theorem can be obtained within the AdS approach, together with a gluon condensate close to the commonly accepted value and robust against perturbation of the background dilaton field.

hep-ph↗
arXiv2009

Rare $B_s$ decays to $η$ and $η^\prime$ final states

We study exclusive $B_s$ decays to final states with $η$ and $η^\prime$, induced by the rare $b \to s \ell^+ \ell^-$ and $b \to s ν\bar ν$ transitions. Differential decay rates and total branching fractions are predicted in the Standard Model, adopting the flavour scheme for the description of the $η$-$η^\prime$ mixing. We discuss the theoretical uncertainty related to the hadronic matrix elements. We also consider these decay modes in a new Physics scenario with a single universal extra dimension, studying the dependence of branching ratios and decay distributions on the compactification scale $R^{-1}$ of the extra dimension.

hep-ph↗
arXiv2008

Light scalar mesons in the soft-wall model of AdS/QCD

We study light scalar mesons in the AdS/QCD soft-wall model with a background dilaton field. The masses and decay constants are compatible with experiment and QCD determinations if $a_0(980)$ and $f_0(980)$ are identified as the lightest scalar mesons; moreover, the states are organized in linear Regge trajectories with the same slope of vector mesons. Comparing the two-point correlation function of scalar operators in AdS and QCD, information about the condensates can be derived. Strong couplings of scalar states to pairs of light pseudoscalar mesons turn out to be small, at odds with experiment and QCD estimates: this discrepancy is related to the description of chiral symmetry breaking in this model.

hep-ph↗
arXiv2008

FCNC $B_s$ and $Λ_b$ transitions: Standard Model versus a single Universal Extra Dimension scenario

We study the FCNC $B_s \to ϕγ, ϕν\bar ν$ and $Λ_b \to Λγ, Λν\bar ν$ transitions in the Standard Model and in a scenario with a single Universal Extra Dimension. In particular, we focus on the present knowledge of the hadronic uncertainties and on possible improvements. We discuss how the measurements of these modes can be used to constrain the new parameter involved in the extra dimensional scenario, the radius $R$ of the extra dimension, completing the information available from B-factories. The rates of these $b \to s$ induced decays are within the reach of new experiments, such as LHCb.

hep-ph↗
arXiv2008

B, D and K decays

With the advent of the LHC, we will be able to probe New Physics (NP) up to energy scales almost one order of magnitude larger than it has been possible with present accelerator facilities. While direct detection of new particles will be the main avenue to establish the presence of NP at the LHC, indirect searches will provide precious complementary information, since most probably it will not be possible to measure the full spectrum of new particles and their couplings through direct production. In particular, precision measurements and computations in the realm of flavour physics are expected to play a key role in constraining the unknown parameters of the Lagrangian of any NP model emerging from direct searches at the LHC. The aim of Working Group 2 was twofold: on one hand, to provide a coherent, up-to-date picture of the status of flavour physics before the start of the LHC; on the other hand, to initiate activities on the path towards integrating information on NP from high-pT and flavour data.

hep-ph↗
arXiv2007

Identifying $D_{sJ}(2700)$ through its decay modes

We study how to assign the recently observed $D_{sJ}(2700)$ meson to an appropriate level of the $c \bar s$ spectrum by the analysis of its decay modes in final states comprising a light pseudoscalar meson. We use an effective lagrangian approach with heavy quark and chiral symmetries, obtaining that the measurement of the $D^* K$ decay width would allow to distinguish between two possible assignments.

hep-ph↗
arXiv2007

Puzzles in charm spectroscopy

We briefly analyze aspects of open and hidden charm resonances, discussing in particular the mesons $D_{sJ}(2860)$ and X(3872).

hep-ph↗
arXiv2007

$X(3872) \to D \bar D γ$ decays and the structure of X(3872)

It has been suggested that the radiative $X \to D \bar D γ$ decay modes are useful to shed light on the structure of the meson X(3872), since the ratio $ R={Γ(X \to D^+ D^- γ) \over Γ(X \to D^0 \bar D^0 γ)}$ is expected to be small ($R \ll 1$) if $X$ is a molecular $D^{*0} \bar D^0$ state. We compute $R$ in a $\bar c c$ $J^{PC}=1^{++}$ description of $X$ finding that it is tiny in a wide range of hadronic parameters governing the decay. A discrimination between the molecular and $\bar c c$ description can be obtained through the analysis of the photon spectrum.

hep-ph↗
arXiv2007

On the light glueball spectrum in a holographic description of QCD

We investigate the spectra of light scalar and vector glueballs in a holografic description of QCD with a dilaton background bulk field. In particular, we study how the glueball masses depend on the conditions on the dilaton background and on the geometry of the bulk.

hep-ph↗
arXiv2006

Spin effects in rare $B \to X_s τ^+ τ^-$ and $B \to K^{(*)} τ^+ τ^-$ decays in a single Universal Extra Dimension scenario

We study the branching fractions and the lepton polarization asymmetries of rare $B \to X_s τ^+ τ^-$ and $B \to K^{(*)} τ^+ τ^-$ modes within the Standard Model and in the Appelquist-Cheng-Dobrescu model, which is a New Physics scenario with a single universal extra dimension. In particular, we investigate the sensitivity of the observables to the radius $R$ of the compactified extra-dimension, which is the only new parameter in this New Physics model. For the exclusive transitions we study the uncertainties due to the hadronic matrix elements using two set of form factors, finding that in many cases such uncertainties are small. In particular, we show that the $τ^-$ polarization asymmetries become free of hadronic uncertainties if Large Energy relations for the form factors, valid for low momentum transfer to the lepton pair, are used. We also consider $K^*$ helicity fractions and their sensitivity to the compactification parameter.

hep-ph↗
arXiv2006

New open and hidden charm spectroscopy

Many new results on open and hidden charm spectroscopy have been obtained recently. We present a short review of the experimental findings in the meson sector, of the theoretical interpretations and of the open problems, with a discussion on the possibility that some mesons are not quark-antiquark states.

hep-ph↗
arXiv2006

Exclusive $B \to K^{(*)} \ell^+ \ell^-$, $B \to K^{(*)} ν{\bar ν}$ and $B \to K^* γ$ transitions in a scenario with a single Universal Extra Dimension

We analyze the exclusive rare $B \to K^{(*)} \ell^+ \ell^-$, $B \to K^{(*)} ν\bar ν$ and $B \to K^* γ$ decays in the Applequist-Cheng-Dobrescu model, which is an extension of the Standard Model in presence of universal extra dimensions. In particular, we consider the case of a single universal extra dimension. We study how spectra, branching fractions and asymmetries depend on the compactification parameter 1/R, and whether the hadronic uncertainty due to the form factors obscures or not such a dependence. We find that, using present data, it is possible in many cases to put a sensible lower bound to 1/R, the most stringent one coming from $B \to K^* γ$. We also study how improved experimental data can be used to establish stronger constraints to this model.

hep-ph↗
arXiv2006

Model independent analysis of a class of $\bar{B}_s^0 $ decay modes

The widths of a class of two-body $\bar{B}_s^0 $ decays induced by $b \to c \bar u d$ and $b \to c \bar u s$ transitions are determined in a model-independent way, using $SU(3)_F$ symmetry and existing information on $\bar B \to D_{(s)} P$ and $\bar B \to D_{(s)} V$ decays, with $P$ and $V$ a light pseudoscalar or vector meson. The results are relevant for the $B_s$ physics programmes at the hadron colliders and at the $e^+ e^-$ factories running at the peak of $Υ(5S)$.

hep-ph↗
arXiv2005

On the structure of $D_{sJ}^*(2317)$ and $D_{sJ}(2460)$

We discuss the structure of the narrow mesons with charm and strangeness $D_{sJ}^*(2317)$ and $D_{sJ}(2460)$, stressing the role of the radiative decay modes in shedding light on the quark content of these states. We argue that present experimental data favour the interpretation of the two states as ordinary $\bar c s$ mesons. We suggest the existence of resonances with similar properties and well predicted masses in the $\bar b s$ sector.

hep-ph↗