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E. Meggiolaro

Publications and source records attributed to E. Meggiolaro.

At least 19 recordsLinked to original sources
arXiv2017

An investigation on the leading and subleading high-energy behavior of hadron-hadron total cross sections using a best-fit analysis of hadronic scattering data

In the present investigation we study the leading and subleading high-energy behavior of hadron-hadron total cross sections using a best-fit analysis of hadronic scattering data. The parametrization used for the hadron-hadron total cross sections at high energy is inspired by recent results obtained by Giordano and Meggiolaro (2014) using a nonperturbative approach in the framework of QCD and it reads $σ_\text{tot} \sim B\ln^2 s + C\ln s\ln\ln s$. Both $B$ and $C$ are obtained by means of best-fits to data for proton-proton and antiproton-proton scattering, including recent data obtained at the LHC, and also to data for other meson-baryon and baryon-baryon scattering processes. The results are compared to the theoretical predictions existing in the literature. In particular, following the above-mentioned nonperturbative QCD approach, we also consider fits where the parameters $B$ and $C$ are set to $B = κB_\text{th}$ and $C = κC_\text{th}$, where $B_\text{th}$ and $C_\text{th}$ are universal quantities related to the QCD stable spectrum, while $κ$ (treated as an extra free parameter) is related to the asymptotic value of the ratio $σ_\text{el}/σ_\text{tot}$. Different possible scenarios are then considered and compared.

hep-ph↗
arXiv2013

Remarks on the U(1) axial symmetry and the chiral transition in QCD at finite temperature

We discuss the role of the U(1) axial symmetry for the scalar and pseudoscalar meson mass spectrum of QCD at finite temperature, above the chiral transition at T_c, using a chiral effective Lagrangian model, which, in addition to the usual chiral condensate, also includes a (possible) genuine U(1)_A-breaking condensate that (possibly) survives across the chiral transition. The motivations for considering this Lagrangian (and a critical comparison with other effective Lagrangian models existing in the literature) are presented. A detailed comparison between the case N_f=3 (or N_f>3) and the (remarkably different) case N_f=2 is performed. The results obtained in the case N_f=2 are also critically compared with the available lattice results.

hep-ph↗
arXiv2013

Asymptotic high-energy behavior of hadronic total cross sections from lattice QCD

We will show how a universal and Froissart-like (i.e., of the kind "B log^2 s") hadron-hadron total cross section can emerge in QCD asymptotically at high energy, finding indications for this behavior from the lattice. The functional integral approach provides the natural setting for achieving this result, since it encodes the energy dependence of hadronic scattering amplitudes in a single elementary object, i.e., a proper correlation function of two Wilson loops.

hep-ph↗
arXiv2012

High-energy behavior of hadronic total cross sections from lattice QCD

By means of a nonperturbative approach to soft high-energy hadron-hadron scattering, based on the analytic continuation of Wilson-loop correlation functions from Euclidean to Minkowskian theory, we shall investigate the asymptotic energy dependence of hadron-hadron total cross sections in lattice QCD: we will show, using best fits of the lattice data with proper functional forms satisfying unitarity and other physical constraints, how indications emerge in favor of a universal asymptotic high-energy behavior of the kind $B \log^2 s$ for hadronic total cross sections.

hep-ph↗
arXiv2011

Hadron-hadron total cross sections and soft high-energy scattering on the lattice

The nonperturbative approach to soft high-energy hadron-hadron scattering, based on the analytic continuation of Euclidean Wilson-loop correlation functions, makes possible the investigation of the problem of the asymptotic energy dependence of hadron-hadron total cross sections by means of lattice calculations. In this contribution we compare the lattice numerical results to analytic results obtained with various nonperturbative techniques. We also discuss the possibility to obtain indications of the rise of hadron-hadron total cross sections with energy directly from the lattice data.

hep-lat↗
arXiv2010

Instanton effects on Wilson-loop correlators: a new comparison with numerical results from the lattice

Instanton effects on the Euclidean correlation function of two Wilson loops at an angle $θ$, relevant to soft high-energy dipole-dipole scattering, are calculated in the Instanton Liquid Model and compared with the existing lattice data. Moreover, the instanton-induced dipole-dipole potential is obtained from the same correlation function at $θ=0$, and compared with preliminary lattice data.

hep-ph↗
arXiv2009

A nonperturbative foundation of the Euclidean-Minkowskian duality of Wilson-loop correlation functions

In this letter we discuss the analyticity properties of the Wilson-loop correlation functions relevant to the problem of soft high-energy scattering, directly at the level of the functional integral, in a genuinely nonperturbative way. The strategy is to start from the Euclidean theory and to push the dependence on the relevant variables $θ$ (the relative angle between the loops) and $T$ (the half-length of the loops) into the action by means of a field and coordinate transformation, and then to allow them to take complex values. In particular, we determine the analyticity domain of the relevant Euclidean correlation function, and we show that the corresponding Minkowskian quantity is recovered with the usual double analytic continuation in $θ$ and $T$ inside this domain. The formal manipulations of the functional integral are justified making use of a lattice regularisation. The new rescaled action so derived could also be used directly to get new insights (from first principles) in the problem of soft high-energy scattering.

hep-ph↗
arXiv2008

High-energy hadron-hadron (dipole-dipole) scattering from lattice QCD

In this paper the problem of high-energy hadron-hadron (dipole-dipole) scattering is approached (for the first time) from the point of view of lattice QCD, by means of Monte Carlo numerical simulations. In the first part, we give a brief review of how high-energy scattering amplitudes can be reconstructed, using a functional-integral approach, in terms of certain correlation functions of two Wilson loops and we also briefly recall some relevant analyticity and crossing-symmetry properties of these loop-loop correlation functions, when going from Euclidean to Minkowskian theory. In the second part, we shall see how these (Euclidean) loop-loop correlation functions can be evaluated in lattice QCD and we shall compare our numerical results with some nonperturbative analytical estimates that appeared in the literature, discussing in particular the question of the analytic continuation from Euclidean to Minkowskian theory and its relation to the still unsolved problem of the asymptotic s-dependence of the hadron-hadron total cross sections.

hep-lat↗
arXiv2007

High-energy scattering and Euclidean-Minkowskian duality

We shall discuss how some relevant analyticity and crossing-symmetry properties of the "eikonal scattering amplitudes" of two Wilson loops in QCD, when going from Euclidean to Minkowskian theory, can be related to the still unsolved problem of the asymptotic s-dependence of the hadron-hadron total cross-sections. In particular, we critically discuss the question if (and how) a pomeron-like behaviour can be derived from this Euclidean-Minkowskian duality.

hep-ph↗
arXiv2007

Can the pomeron be derived from a Euclidean-Minkowskian duality?

After a brief review, in the first part, of some relevant analyticity and crossing-symmetry properties of the correlation functions of two Wilson loops in QCD, when going from Euclidean to Minkowskian theory, in the second part we shall see how these properties can be related to the still unsolved problem of the asymptotic s-dependence of the hadron-hadron total cross sections. In particular, we critically discuss the question if (and how) a pomeron-like behaviour can be derived from this Euclidean-Minkowskian duality.

hep-ph↗
arXiv2006

Analyticity and crossing symmetry of the eikonal amplitudes in gauge theories

After a brief review and a more refined analysis of some relevant analyticity properties (when going from Minkowskian to Euclidean theory) of the high-energy parton-parton and hadron-hadron scattering amplitudes in gauge theories, described nonperturbatively, in the eikonal approximation, by certain correlation functions of two Wilson lines or two Wilson loops near the light cone, we shall see how these same properties lead to a nice geometrical interpretation of the crossing symmetry between quark-quark and quark-antiquark eikonal amplitudes and also between loop-loop eikonal amplitudes. This relation between Minkowskian-to-Euclidean analyticity properties and crossing symmetry is discussed in detail and explicitly tested in the first orders of perturbation theory. Some nonperturbative examples existing in the literature are also discussed.

hep-ph↗
arXiv2005

Dynamics of quark-gluon plasma from Field correlators

It is argued that strong dynamics in the quark-gluon plasma and bound states of quarks and gluons is mostly due to nonperturbative effects described by field correlators. The emphasis in the paper is made on two explicit calculations of these effects from the first principles: one analytic using gluelump Green's functions and another using independent lattice data on correlators. The resulting hadron spectra are investigated in the range T_c < T < 2T_c. The spectra of charmonia, bottomonia, light s-sbar mesons, glueballs and quark-gluon states calculated numerically are in general agreement with lattice MEM data. The possible role of these bound states in the thermodynamics of quark-gluon plasma is discussed.

hep-ph↗
arXiv2005

Deriving the pomeron from a Euclidean-Minkowskian duality

After a brief review, in the first part, of some relevant analyticity properties of the loop-loop scattering amplitudes in gauge theories, when going from Minkowskian to Euclidean theory, in the second part we shall see how they can be related to the still unsolved problem of the s-dependence of the hadron-hadron total cross-sections.

hep-ph↗
arXiv2005

Euclidean formulation of diffractive scattering

After a brief review (in the first part) of some relevant properties of the high-energy parton-parton scattering amplitudes, in the second part we shall discuss the infrared finiteness and some analyticity properties of the loop-loop scattering amplitudes in gauge theories, when going from Minkowskian to Euclidean theory, and we shall see how they can be related to the still unsolved problem of the s-dependence of the hadron-hadron total cross-sections.

hep-ph↗