Wanda Maria Alberico

Wanda Maria Alberico
Università degli Studi di Torino | UNITO · Department of Physics

About

174
Publications
6,152
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4,147
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September 1977 - present
Università degli Studi di Torino
Position
  • Professor (Full)

Publications

Publications (174)
Article
Full-text available
A review of the problems of neutrino mass, mixing and oscillations is given. Possible phenomenological schemes of neutrino mixing are discussed. The most important consequences of neutrino mixing-neutrino oscillations are considered in some detail. The data of atmospheric, solar and LSND experiments are discussed. The results of phenomenological an...
Preprint
Full-text available
The QCD transition from a hadronic to a quark-gluon plasma phase is a cross-over at vanishing/small baryo-chemical potential, while at higher chemical potentials it is argued that it becomes of first order, ending with a critical end-point. The present goal is the determination of the critical line and, possibly, the recognition of the critical end...
Preprint
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The evolution of the fireball in heavy ion collisions is an isentropic process, meaning that it follows a trajectory of constant entropy per baryon in the phase diagram of the strong interaction. Responsible for the collective acceleration of the fireball is the speed of sound of the system, while fluctuations of conserved charges are encoded in qu...
Article
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The Rooted Maps Theory, a branch of the Theory of Homology, is shown to be a powerful tool for investigating the topological properties of Feynman diagrams, related to the single particle propagator in the quantum many-body systems. The numerical correspondence between the number of this class of Feynman diagrams as a function of perturbative order...
Article
When the multiplicities of particles produced in heavy-ion collisions are fitted to the hadron-resonance-gas model, excluded-volume effects play a significant role. In this work, we study the impact of such effects onto the equation of state of pure Yang-Mills theory at low temperatures, comparing the predictions of the statistical model with latti...
Article
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This document was prepared by the community that is active in Italy, within INFN (Istituto Nazionale di Fisica Nucleare), in the field of ultra-relativistic heavy-ion collisions. The experimental study of the phase diagram of strongly-interacting matter and of the Quark-Gluon Plasma (QGP) deconfined state will proceed, in the next 10-15 years, alon...
Article
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We present a preliminary analysis on the sensitivity to the chemical freeze-out temperature of higher order moments of strange particle multiplicity distributions in heavy ion collisions. Within the Hadron Resonance Gas (HRG) model we evaluate ratios of cumulants for kaons (K±) and hyperons (Λ, Σ±, Ξ−,0, Ω−) as a function of the temperature and com...
Article
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Fluctuations of conserved charges measured in Heavy-Ion Collisions (HICs) received increasing attention in recent years, because they are good candidates to explore the phase diagram of QCD matter. During the last year, net-electric charge and net-proton moments of multiplicities measured at RHIC have been published by the STAR collaboration, for a...
Article
We present an analysis of fluctuations of conserved charges, as baryon number B and electric charge Q, using the Hadron Resonance Gas (HRG) model. The study of such observables within a theoretical approach and the comparison to experimental data on the moments of the multiplicity distributions of specific particles represents a useful tool to extr...
Article
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We discuss details of our thermal model applied to extract chemical freeze-out conditions from fluctuations in the net-electric charge and net-proton number measured at RHIC. A parametrization for these conditions as a function of the beam energy is given.
Article
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We evaluate and discuss the impact of meson-exchange currents (MEC) on charged-current quasielastic (QE) neutrino cross sections. We consider the nuclear transverse response arising from 2p-2h states excited by the action of electromagnetic, purely isovector meson-exchange currents in a fully relativistic framework, based on the work by the Torino...
Article
We extract chemical freeze-out conditions via a thermal model approach from fluctuation observables measured at RHIC and compare with results from lattice QCD and statistical hadronization model fits. The possible influence of additional critical and non-critical fluctuation sources not accounted for in our analysis is discussed.
Article
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We calculate various equations of state for QCD matter at vanishing net-baryon density starting from recent lattice QCD results at high temperatures, going to low temperatures using a hadron resonance gas (HRG) model to describe the confined phase. In order to have a better description of the experimental situation we use an implementation of the H...
Article
A multi-step setup for heavy-flavour studies in high-energy nucleus–nucleus collisions is presented. The initial hard production of QQ¯ pairs is simulated with the POWHEG pQCD event generator, interfaced with the PYTHIA parton shower. In a nucleus–nucleus collision the propagation of the heavy quarks in the medium is described through the relativis...
Article
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We propose measurements of fluctuation observables, which are sensitive to the chemical freeze-out of the matter produced in heavy-ion collisions, in order to discriminate a potential flavor-specific behavior of light and strange quarks at the QCD confinement transition. This complements our former considerations which were restricted to the strang...
Article
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A multi-step setup for heavy-flavor studies in high-energy nucleus-nucleus (AA) collisions - addressing within a comprehensive framework the initial Q (Q) over bar production, the propagation in the hot medium until decoupling and the final hadronization and decays - is presented. The propagation of the heavy quarks in the medium is described in a...
Article
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We calculate ratios of higher-order susceptibilities quantifying fluctuations in the number of net protons and in the net-electric charge using the Hadron Resonance Gas (HRG) model. We take into account the effect of resonance decays, the kinematic acceptance cuts in rapidity, pseudo-rapidity and transverse momentum used in the experimental analysi...
Article
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We present a quasiparticle model for the pure gauge sector of QCD, in which transverse quasigluons propagate in a Polyakov loop background field. By incorporating thermodynamic self-consistency in the approach, we show that our Polyakov loop extended quasiparticle model allows an accurate description of recent lattice results for all the thermodyna...
Article
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We extend a previous work on the study of heavy charmonia and bottomonia in a deconfined quark-gluon plasma by considering the Bc family of mesons. With the introduction of this bound state of a charm and a beauty quark, we investigate at finite temperature the behavior of the quarkonium, in an energy region between the {\psi} and the {\Upsilon} st...
Article
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A snapshot of the results for heavy-flavour observables in heavy-ion (AA) collisions at RHIC and LHC obtained with our transport calculations is displayed. The initial charm and beauty production is simulated through pQCD tools (POWHEG+PYTHIA) and is validated through the comparison with data from pp collisions. The propagation of c and b quarks in...
Article
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We construct a realistic equation of state for QCD matter at vanishing net-baryon density, which is based on recent lattice QCD results at high temperatures combined with a hadron resonance gas model in the low-temperature, confined phase. Partial chemical equilibrium, in which certain particle ratios are fixed at the chemical freeze-out, can be im...
Article
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A multi-step setup for heavy-flavor studies in high-energy nucleus-nucleus (AA) collisions—addressing within a comprehensive framework the initial \(Q\overline{Q}\) production, the propagation in the hot medium until decoupling and the final hadronization and decays—is presented. The initial hard production of \(Q\overline{Q}\) pairs is simulated u...
Article
We discuss an experimental test of a possible flavor-hierarchy in the confinement transition of QCD based on quark-number susceptibilities. These fluctuation observables are sensitive to a flavor-specific freeze-out behavior. In this work, we concentrate on the study of the strange-quark sector and investigate the influence of acceptance cuts on ou...
Article
The quark-gluon plasma (QGP) excitations, corresponding to the scalar and pseudoscalar meson quantum numbers, for different temperatures are calculated. Analysis is performed in the Hard Thermal Loop (HTL) Approximation and leads to a better understanding of the excitations of QGP in the deconfined phase and is also of relevance for lattice studies...
Article
A refined version of a multi-step calculation of heavy-flavor observables in pp and AA collisions has been developed, based on pQCD at NLO accuracy followed by parton shower evolution to describe heavy-quark production and on the relativistic Langevin equation to describe their stochastic evolution in the QCD plasma. Then, hadronization is modeled...
Article
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We study the stochastic dynamics of c and b quarks, produced in hard initial processes, in the hot medium created after the collision of two relativistic heavy ions. This is done through the numerical solution of the relativistic Langevin equation. The latter requires the knowledge of the friction and diffusion coefficients, whose microscopic evalu...
Article
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The stochastic dynamics of c and b quarks in the fireball created in nucleus-nucleus collisions at RHIC and LHC is studied employing a relativistic Langevin equation, based on a picture of multiple uncorrelated random collisions with the medium. Heavy-quark transport coefficients are evaluated within a pQCD approach, with a proper HTL resummation o...
Article
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We present a study of the heavy-flavor dynamics in nucleus-nucleus collisions. The initial (hard) production of c and b quarks is taken from NLO pQCD predictions. The presence of a hot medium (a Quark Gluon Plasma described by hydrodynamics) affects the final spectra of open-charm (beauty) hadrons and their decay electrons with respect to what foun...
Article
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The thermodynamic behavior of QCD matter at high temperature is currently studied by lattice QCD theory. The main features are the fast rise of the energy density $\epsilon$ around the critical temperature $T_c$ and the large trace anomaly of the energy momentum tensor $< \Theta_\mu^\mu >=\epsilon - 3 P$ which hints at a strongly interacting system...
Article
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The propagation of the heavy quarks produced in relativistic nucleus-nucleus collisions at RHIC and LHC is studied within the framework of Langevin dynamics in the background of an expanding deconfined medium described by ideal and viscous hydrodynamics. The transport coefficients entering into the relativistic Langevin equation are evaluated by ma...
Article
We study the stochastic dynamics of c and b quarks in the hot plasma produced in nucleus-nucleus collisions at RHIC and LHC, providing results for the nuclear modification factor RAA and the elliptic flow coefficient v2 of the single-electron spectra arising from their semi-leptonic decays. The initial pairs are generated using the POWHEG code, imp...
Article
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The stochastic dynamics of heavy quarks in the fireball produced in heavy-ion collisions is followed through numerical simulations based on the Langevin equation. The modification of the final p_T spectra (R_AA) of c and b quarks, hadrons and single-electrons with respect to pp collisions is studied. The transport coefficients are evaluated treatin...
Article
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The effects of the Polyakov loop and of a regularization procedure that allows the presence of high momentum quark states at finite temperature is investigated within the Polyakov-loop extended Nambu--Jona-Lasinio model. The characteristic temperatures, as well as the behavior of observables that signal deconfinement and restoration of chiral and a...
Article
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Electromagnetic form factors of proton and neutron, obtained from a new fit of data, are presented. The proton form factors are obtained from a simultaneous fit to the ratio mu(p)G(Ep)/G(Mp) determined from polarization transfer measurements and to ep elastic cross section data. Phenomenological two-photon exchange corrections are taken into accoun...
Article
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We investigate the modifications of mesonic properties in a hot medium having in mind to use the mesonic modes as a tool to analyze the restoration of chiral and axial symmetries in the context of the SU(3) Polyakov--Nambu--Jona-Lasinio (PNJL) model. The results lead to the conclusion that the effects of the Polyakov loop are fundamental for reprod...
Article
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We present predictions for the value of the cross section ratio $\sigma(e^+p \to e^+p)/\sigma(e^-p \to e^-p)$, determined from our fit of the elastic $ep$ cross section and polarization data. In this fit we took into account the phenomenological two-photon exchange dispersive correction. The cross section ratios which are expected to be measured by...
Article
Quark Gluon Plasma transport coefficients for heavy quarks and pairs are computed through an extension of the results obtained for a hot QED plasma by describing the heavy-quark propagation in the eikonal approximation and by weighting the gauge-field configurations with the Hard Thermal Loop effective action. It is shown that such a model allows t...
Article
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Following the basic prescriptions of the relativistic Tsallis' non-extensive thermostatistics, we investigate from a phenomenological point of view the relevance of non-extensive statistical effects on relativistic heavy-ion collisions observable, such as rapidity spectra of net proton production, transverse momentum distributions and transverse mo...
Article
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The quark viscosity in the quark–gluon plasma is evaluated in the hard thermal loop (HTL) approximation. The different contributions to the viscosity arising from the various components of the quark spectral function are discussed. The calculation is extended to finite values of the chemical potential.
Article
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We consider the shear viscosity of a system of quarks and its ratio to the entropy density above the critical temperature for deconfinement. Expressions for both quantities are derived in the quasi-particle approximation and calculations are carried out for different modeling of the quark self-energy, also allowing for a temperature dependence of t...
Article
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The modification of mesonic observables in a hot medium is analyzed as a tool to investigate the restoration of chiral and axial symmetries in the context of the Polyakov-loop extended Nambu–Jona-Lasinio model. The results of the extended model lead to the conclusion that the effects of the Polyakov loop are fundamental for reproducing lattice find...
Chapter
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A review of the problems of neutrino mass, mixing and oscillations is given. Possible phenomenological schemes of neutrino mixing are discussed. The most important consequences of neutrino mixing-neutrino oscillations are considered in some detail. The data of atmospheric, solar and LSND experiments are discussed. The results of phenomenological an...
Article
We re-examine the charge longitudinal response, as measured in inelastic electron scattering, within the framework of a semi-classical RPA theory, utilizing a Skyrme force. The effects of the Hartree-Fock field are analysed. A comparison with an exact RPA calculation is presented.
Article
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We update our recent calculation of quarkonium Euclidean correlators at finite temperatures in a potential model by including the effect of zero modes in the lattice spectral functions. These contributions cure most of the previously observed discrepancies with lattice calculations, supporting the use of potential models at finite temperature as an...
Article
The meson screening mass in the pseudoscalar channel is calculated from the momentum dependent meson spectral function, using HTL fermionic propagators. A careful subtraction procedure is required to get an UV finite result. It is shown that in the whole range of temperatures explored here the HTL screening mass stays above the non-interacting resu...
Article
The use of the Boson Loop Expansion is proposed for investigating the static properties of nuclear matter. We explicitly consider a schematic dynamical model in which nucleons interact with the scalar–isoscalar σ meson. The suggested approximation scheme is examined in detail at the mean field level and at the one- and two-loop orders. The relevant...
Article
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The Schroedinger equation for the charmonium and bottomonium states at finite temperature is solved by employing an effective temperature dependent potential given by a linear combination of the color singlet free and internal energies obtained on the lattice from the Polyakov loop correlation functions. The melting temperatures and other propertie...
Article
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We investigate the properties of scalar and pseudo-scalar mesons at finite temperature and quark chemical potential in the framework of the Nambu-Jona-Lasinio (NJL) model coupled to the Polyakov loop (PNJL model) with the aim of taking into account features of both chiral symmetry breaking and deconfinement. The mesonic correlators are obtained by...
Article
We consider different methods and observables which can be obtained by the measurement of neutrino scattering off nucleons and nuclei with the purpose of finding evidence for the strange form factors of the nucleon, which enter into structure of the nucleonic weak neutral current.
Article
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Some progress experienced recently in the field of hypernuclear weak decay is briefly summarized. Theoretical analyses of the double‐coincidence nucleon spectra measured at KEK points towards a solution of the long‐standing puzzle on the ratio Γ n /Γ p between the neutron‐(Λn → nn) and proton‐induced (Λp → np) decay rates. Despite this improvement,...
Article
The finite momentum meson spectral function (MSF) in the pseudoscalar channel is evaluated, adopting for the fermionic propagators HTL expressions. The different contributions to the meson spectral functions are clearly displayed. Our analysis may be of relevance for lattice studies of MSF based so far on the maximum entropy method. As a further st...
Article
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A comprehensive parametrization of the color-singlet heavy quark free energy above T{sub c} is given, using the lattice data in quenched (N{sub f}=0) and unquenched (N{sub f}=2 and N{sub f}=3) QCD. The corresponding (temperature dependent) potentials thus obtained are then inserted into the Schroedinger equation for charmonium and bottomonium in th...
Article
Starting from the presence of non-ideal plasma effects due to strongly coupled plasma in the early stage of relativistic heavy-ion collisions, we investigate, from a phenomenological point of view, the relevance of non-conventional statistical mechanics effects on the rapidity spectra of net proton yield at AGS, SPS and RHIC. We show that the broad...
Article
We shortly review the open problems in the physics of the weak decay of Λ-hypernuclei. For many years the main question has been the discrepancy between theory and experiment for the ratio Γn/Γp between the neutron- (Λn → nn) and proton-induced (Λp → np) decay rates. Recent indications towards a solution of the puzzle are discussed here. The other...
Article
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The nonmesonic weak decay of polarized Lambda hypernuclei is studied for the first time by taking into account, with a Monte Carlo intranuclear cascade code, the nucleon final state interactions. A one-meson-exchange model is employed to describe the Lambda-->N-->nN processes in a finite nucleus framework. The relationship between the intrinsic Lam...
Article
The temporal pseudoscalar meson correlation function in a QCD plasma is investigated in a range of temperatures exceeding $T_c$ and yet of experimental interest. Only the flavour-singlet channel is considered and the imaginary time formalism is employed for the finite temperature calculations. The behaviour of the meson spectral function and of the...
Article
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The focus of these Lectures is on the weak decay modes of hypernuclei, with special attention to Lambda-hypernuclei. The subject involves many fields of modern theoretical and experimental physics, from nuclear structure to the fundamental constituents of matter and their interactions. The various weak decay modes of Lambda-hypernuclei are describe...
Article
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In this contribution we discuss an evaluation of double-nucleon coincidence spectra for the non-mesonic weak decay of Lambda-hypernuclei. The results have been obtained by combining a one-meson-exchange model for the Lambda N -> nN transition in finite nuclei with a Monte Carlo code accounting for the nucleon final state interactions. A weak-decay-...
Article
Following recent studies of inclusive electron scattering from nuclei at high energies which focused on two-nucleon emission mediated by meson-exchange currents, in this work the superscaling behavior of such contributions is investigated. Comparisons are made with existing data below the quasielastic peak where at high momentum transfers scaling o...
Article
We review the mechanism of weak decay of hypernuclei, with emphasis on the non-mesonic decay channels. Various theoretical approaches are discussed and the results are compared with the available experimental data.
Article
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The possibility to determine the axial strange form factor of the nucleon from elastic neutrino-nucleon scattering experiments is studied. The existing experimental information is shortly mentioned and several observables which could be measured in the near future at new neutrino facilities are discussed. Comment: 6 pages, 1 figure, contribution to...
Article
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The original B. Pontecorvo idea of neutrino oscillations is discussed. Neutrino mixing and basics of neutrino oscillations in vacuum and in matter are considered. Recent evidences in favour of neutrino oscillations, obtained in Super-Kamiokande, SNO, KamLAND and other neutrino experiments are discussed. Neutrino oscillations in the solar and atmosp...
Article
The contribution to the nuclear transverse response function R_T arising from two particle-two hole (2p-2h) states excited through the action of electromagnetic meson exchange currents (MEC) is computed in a fully relativistic framework. The MEC considered are those carried by the pion and by Delta degrees of freedom, the latter being viewed as a v...