arXiv subjects

Floriana Giannuzzi

Publications and source records attributed to Floriana Giannuzzi.

At least 19 recordsLinked to original sources

arXiv2026

Vector-meson properties in a data-driven AdS/QCD model

We investigate the properties of $ρ$, $ψ$, and $Υ$ mesons within a holographic AdS/QCD framework, capturing both their vacuum phenomenology and in-medium dynamics. By reconstructing flavor-specific gauge kinetic functions within a model originally developed to study thermodynamic functions, we compute the vector-meson mass spectrum, the decay constants and the hadronic vacuum polarization contributions to the anomalous magnetic moment of the muon at zero temperature. Furthermore, we evaluate the thermal spectral functions to analyze mass shifts, resonance broadening, and the melting of vector bound states in a hot and dense medium. Finally, using the Kubo formula, we extract the electrical conductivity of the plasma as a function of temperature and chemical potential.

hep-ph↗

arXiv2025

Data-Driven Refinement of an Analytical Holographic Model for the QCD Phase Transition

Using (2+1)-flavor lattice QCD data, we refine the parameters of an analytical holographic model via gradient descent optimization to precisely locate the critical endpoint in the $T-μ$ plane. Specifically, we calibrate the model using input data for the speed of sound at $μ_B = 0$, the second-order baryon number susceptibility $χ^B_2$, and the baryon number density at $μ_B/T = 1$. With these parameters fixed, we calculate pressure and energy density versus temperature at small chemical potentials and compare the results with lattice QCD data using Taylor expansion techniques. This comparison validates the robustness of our model upon extension to finite chemical potentials, as the results show broad consistency with lattice QCD data in this regime. Finally, we employ the calibrated model to determine the coordinates of the critical endpoint in the $T-μ_B$ plane, finding it located at $(μ_B = 0.678 \, \rm{GeV}, T = 0.110 \, \rm{GeV})$

hep-ph↗

arXiv2025

Out-of-equilibrium chiral condensate in AdS/QCD

We study the chiral condensate at finite temperature in AdS/QCD in a time-dependent background, in which the position of the black-hole horizon $z_h$ changes with time, producing an increasing or decreasing temperature. Conformal invariance is broken, as in the soft-wall model, by a static quadratic dilaton. Two different scenarios are analysed: in the first a general power-law time dependence is assumed for $z_h$, while in the second the energy-momentum tensor at late times reproduces the one found in viscous hydrodynamics. Depending on the rate at which the system evolves, the transition shifts toward lower temperatures. If the chiral condensate is far from equilibrium at low temperatures, oscillations around its equilibrium value are observed before thermalization. A prethermalization stage is found in the chiral limit if the initial condition is set at a temperature close to the critical one. In the hydrodynamic setup the evolution of the medium is slow enough, and the chiral condensate soon matches the equilibrium curve.

hep-ph↗

arXiv2024

Exotic spectroscopy in a diquark model with a little help from AdS/QCD

Masses of heavy mesons, tetraquarks and pentaquarks computed in a potential model are shown. Tetraquarks are studied as bound states of a diquark and an antidiquark. Pentaquarks are constructed from a series of two-body interactions between the four quarks and the antiquark. New results on $Qs\bar Q \bar q$ and $QQ\bar Q \bar Q$ tetraquarks are also obtained.

hep-ph↗

arXiv2024

Hadronic light-by-light scattering contributions to $(g-2)_μ$ from axial-vector and tensor mesons in the holographic soft-wall model

We compute the light axial-vector and tensor meson two-photon transition form factors in the soft-wall holographic model of QCD in the flavor-symmetric case. They are used to evaluate the axial-vector and tensor meson contributions to the anomalous magnetic moment of the muon via the hadronic light-by-light scattering process. As expected, these contributions are smaller than the one from pseudoscalar mesons. The result for axial-vector mesons is higher than the value found in other approaches.

hep-ph↗

arXiv2023

$π^0, η, η^\prime$ two-photon transition form factors in the holographic soft-wall model and contributions to $(g-2)_μ$

We compute the two-photon transition form factors of the light pseudoscalar $π^0$, $η$ and $η^\prime$ mesons in a soft-wall holographic model of QCD with a solution of the $U(1)_A$ problem. We compare the results with the experimental data in different ranges of photon virtualities. The obtained transition form factors are used to determine the $π^0$, $η$ and $η^\prime$ pole terms in the hadronic light-by-light scattering contribution to the anomalous magnetic moment of the muon.

hep-ph↗

arXiv2021

Chaotic dynamics of a suspended string in a gravitational background with magnetic field

We study the effects of a magnetic field on the chaotic dynamics of a string with endpoints on the boundary of an asymptotically AdS$_5$ space with black hole. We study Poincaré sections and compute the Lyapunov exponents for the string perturbed from the static configuration, for two different orientations, with position of the endpoints on the boundary orthogonal and parallel to the magnetic field. We find that the magnetic field stabilizes the string dynamics, with the largest Lyapunov exponent remaining below the Maldacena-Shenker-Stanford bound.

hep-th↗

arXiv2021

$U(1)_A$ axial anomaly, $η^\prime$, and topological susceptibility in the holographic soft-wall model

The singlet pseudoscalar sector of light mesons is investigated in the soft-wall model, a bottom-up approach to the AdS/QCD correspondence. The $η^\prime$ mass results from the mixing among the fields dual to the axial current, pseudoscalar current and the $G\tilde G$ operator. The topological susceptibility is computed for any quark mass, and the Witten-Veneziano relation is obtained in the large $N_c$ limit.

hep-ph↗

arXiv2019

Holographic thermalisation of strongly-coupled systems

The thermalisation of a strongly-coupled plasma is studied through the AdS/CFT correspondence. The system starts behaving as in viscous hydrodynamics shortly after the end of the perturbation. Local and nonlocal probes are used to characterise the process towards equilibrium.

hep-ph↗

arXiv2019

Heavy pentaquark spectroscopy in the diquark model

$QQ^\prime qq\bar q$ pentaquarks are studied in a potential model, under the hypothesis that they are composite objects of two diquarks and one antiquark. The interaction between two colored objects includes two contributions, one based on the $q\bar q$ potential in QCD, computed in the gauge/string duality approach, and another describing the spin-spin interaction. The model has been extended to investigate pentaquarks with different quark content, as $Qqqq\bar q$ and $Qqqq\bar Q$, the latter including the states observed by LHCb, $P_c(4380)^+$ and $P_c(4450)^+$, later updated, with a new data sample, to $P_c(4312)^+$, $P_c(4440)^+$, and $P_c(4457)^+$.

hep-ph↗

arXiv2016

Role of nonlocal probes of thermalization for a strongly interacting non-Abelian plasma

We use a holographic method to investigate thermalization of a boost-invariant strongly interacting non-Abelian plasma. Boundary sourcing, a distorsion of the boundary metric, is employed to drive the system far from equilibrium. Thermalization is analyzed through nonlocal probes: the equal-time two-point correlation function of large conformal dimension operators in the boundary theory, and Wilson loops of different shapes. We study the dependence of the thermalization time on the size of the probes, and compare the results to the ones obtained using local observables: the onset of thermalization is first observed at short distances.

hep-ph↗

arXiv2015

Thermalization of a boost-invariant non-Abelian plasma: Holographic approach with boundary sourcing

In a holographic approach, the evolution of a 4D strongly coupled non-Abelian plasma towards equilibrium can be studied investigating a 5D gravitational dual. The process driving the plasma out-of-equilibrium can be described by boundary sourcing, a deformation of the boundary metric; the analysis of the late-time dynamics allows to understand how the hydrodynamic regime settles in. We apply the method to a boost-invariant case, considering the effects of different quenches, solving the Einstein equations in the bulk and studying the time-dependence of observables such as the effective temperature, the energy density and the pressures. The main outcome is that, if the effective temperature of the system when the quench is switched off is $T_{eff}(τ^*)=500$ MeV, thermalization is reached within a time of ${\cal O}$(1 fm/c), an important information if the case of the QCD plasma produced in relativistic heavy ion collisions is considered.

hep-ph↗

arXiv2014

Gluon Condensate at finite temperature and density in holographic QCD

The lowest dimensional gluon condensate $G_2$ is analysed at finite temperature and chemical potential using a bottom/up holographic model of QCD. Starting from the free energy of the model, pressure, entropy and quark density are obtained. Moreover, at zero chemical potential, the temporal and spatial Wilson loops at low temperature are computed; they are related to the (chromo-)electric and magnetic components of $G_2$, respectively.

hep-ph↗

arXiv2014

Exotic $J^{PC}=1^{-+}$ mesons in a holographic model of QCD

Mesons with quantum numbers $J^{PC}=1^{-+}$ cannot be represented as simple quark-antiquark pairs. We explore hybrid configurations in the light meson sector comprising a quark, an antiquark and an excited gluon, studying the properties of such states in a phenomenological model inspired by the gauge/gravity correspondence. The computed mass, compared to the experimental mass of the $1^{-+}$ candidates $π_1(1400)$, $π_1(1600)$ and $π_1(2015)$, favous $π_1(1400)$ as the lightest hybrid state. An interesting result concerns the stability of hybrid mesons at finite temperature: they disappear from the spectral function (i.e. they melt) at a lower temperature with respect to other states, light vector and scalar mesons, and scalar glueballs.

hep-ph↗

arXiv2014

Temperature and chemical potential dependence of the gluon condensate: a holographic study

The lowest dimensional gluon condensate $G_2$ is analyzed at finite temperature and chemical potential using a holographic model of QCD with conformal invariance broken by a background dilaton. Starting from the free energy of the model, the thermodynamical quantities needed to determine the $T$ and $μ$ dependence of the gluon condensate are evaluated. At high temperature the gluon condensate is independent of chemical potential. Moreover, at $μ=0$ and in the string frame, the temporal and spatial Wilson loops at low temperature are computed; they are related to the (chromo) electric and magnetic components of $G_2$, respectively. The $T$-dependence of the two components is separately determined.

hep-ph↗

arXiv2013

New results in open charm spectroscopy through an effective Lagrangian approach

An effective Lagrangian approach based on the heavy quark and chiral symmetry is introduced to analyse the spectroscopy of open charm mesons. Strong two-body decay widths and ratios of branching fractions are computed, and this piece of information is used to assign quantum numbers to recently observed charmed states which still need to be properly classified.

hep-ph↗

arXiv2013

Heavy Quarkonium moving in a Quark-Gluon Plasma

By means of effective field theory techniques, we study the modifications of some properties of weakly coupled heavy quarkonium states propagating through a quark-gluon plasma at temperatures much smaller than the heavy quark mass, m_Q. Two different cases are considered, corresponding to two different hierarchies between the typical size of the bound state, r, the binding energy, E, the temperature, T, and the screening mass, m_D. The first case corresponds to the hierarchy m_Q >> 1/r >> T >> E >> m_D, relevant for moderate temperatures, and the second one to the hierarchy m_Q >> T >> 1/r, m_D >> E, relevant for studying the dissociation mechanism. In the first case we determine the perturbative correction to the binding energy and to the decay width of states with arbitrary angular momentum, finding that the width is a decreasing function of the velocity. A different behavior characterizes the second kinematical case, being the width of s-wave states a non-monotonic function of the velocity, increasing at moderate velocities and decreasing in the ultra-relativistic limit. We obtain a simple analytical expression of the decay width for T >> 1/r >> m_D >> E at moderate velocities, and we derive the s-wave spectral function for the more general case T >> 1/r, m_D >> E. A brief discussion of the possible experimental signatures as well as a comparison with the relevant lattice data are also presented.

hep-ph↗

arXiv2012

Holographic vector mesons in a hot and dense medium

We investigate vector meson spectral functions at finite temperature and density through the soft wall model, a bottom-up holographic approach to QCD. We find narrow resonances at small values of the parameters, becoming broader as temperature and density increase. We study dissociation of such states, occurring when no peak can be distinguished in the spectral function. We also find a decreasing of the mass of vector mesons at increasing temperature and density. Finally, a discussion of these results is presented.

hep-ph↗