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Alessandro Papa

Publications and source records attributed to Alessandro Papa.

At least 73 records · Page 4Linked to original sources

Three-quark potentials in an $SU(3)$ effective Polyakov loop model

Three-quark potentials are studied in great details in the three-dimensional $SU(3)$ pure gauge theory at finite temperature, for the cases of static sources in the fundamental and adjoint representations. For this purpose, the corresponding Polyakov loop model in its simplest version is adopted. The potentials in question, as well as the conventional quark--anti-quark potentials, are calculated numerically both in the confinement and deconfinement phases. Results are compared to available analytical predictions at strong coupling and in the limit of large number of colors $N$. The three-quark potential is tested against the expected $Δ$ and $Y$ laws and the $3q$ string tension entering these laws is compared to the conventional $q\bar{q}$ string tension. As a byproduct of this investigation, essential features of the critical behaviour across the deconfinement transition are elucidated.

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Unintegrated gluon distribution from forward polarized $ρ$-electroproduction

We present here some arguments to support our suggestion that data on the helicity structure for the hard exclusive electroproduction of $ρ$ mesons at HERA (and in possible future high-energy electron-proton colliders) provide useful information to constrain the $κ$-shape of the unintegrated gluon distribution in the proton.

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Finite density 2d O(3) sigma model: dualization and numerical simulations

The action of the 2d O(3) non-linear sigma model on the lattice in a bath of particles, when expressed in terms of standard O(3) degrees of freedom, is complex. A reformulation of the model in terms of new variables that makes the action real is presented. This reshaping enables us to utilize Monte Carlo simulations based on usual importance sampling. Several observables, including the correlation function and the mass gap, are measured.

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Spatial structure of the color field in the SU(3) flux tube

We report on the chromoelectric and chromomagnetic fields generated by a static quark-antiquark pair at zero temperature in pure gauge SU(3). From the spatial structure of chromoelectric field we extract its nonperturbative part and discuss its properties.

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Hadron-jet correlations in high-energy hadronic collisions at the LHC

The inclusive production at the LHC of a charged light hadron and of a jet, featuring a wide separation in rapidity, is suggested as a new probe process for the investigation of the BFKL mechanism of resummation of energy logarithms in the QCD perturbative series. We present some predictions, tailored on the CMS and CASTOR acceptances, for the cross section averaged over the azimuthal angle between the identified jet and hadron and for azimuthal correlations.

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$ρ$-meson leptoproduction as testfield for the unintegrated gluon distribution in the proton

The gluon content of the proton is embodied by the unintegrated gluon distribution (UGD), which has universal validity. In literature many models of UGD have been proposed so far. The polarized $ρ$-meson leptoproduction at HERA offers a nowadays unexplored testfield to discriminate among existing models of UGD, via the comparison with theoretical predictions formulated in the $κ$-factorization approach.

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High-energy resummation in heavy-quark pair photoproduction

We present our predictions for the inclusive production of two heavy quark-antiquark pairs, separated by a large rapidity interval, in the collision of (quasi-)real photons at the energies of LEP2 and of some future electron-positron colliders. We include in our calculation the full resummation of leading logarithms in the center-of-mass energy and a partial resummation of the next-to-leading logarithms, within the Balitsky-Fadin-Kuraev-Lipatov (BFKL) approach.

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QCD flux tubes across the deconfinement phase transition

We study the behavior across the deconfinement phase transition of the chromoelectric flux tube generated by a static quark and a static antiquark for several distances between them. We present preliminary results for distances up to 1.33 fm and temperatures up to $1.5 T_c$.

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Inclusive dihadron production at the LHC in NLA BFKL

A study of cross sections and azimuthal correlation moments for the inclusive production of two, light charged hadrons featuring large transverse momenta and well separated in rapidity at LHC energies, including BFKL resummation effects with NLA accuracy, is presented. This reaction shares the same theoretical setup with the well konwn Mueller-Navelet jet production and can be thought of as a new and complementary channel to access the BFKL dynamics at proton colliders.

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Flux tubes in the QCD vacuum

The hypothesis that the QCD vacuum can be modeled as a dual superconductor is a powerful tool to describe the distribution of the color field generated by a quark-antiquark static pair and, as such, can provide useful clues for the understanding of confinement. In this work we investigate, by lattice Monte Carlo simulations of the $SU(3)$ pure gauge theory and of (2+1)-flavor QCD with physical mass settings, some properties of the chromoelectric flux tube at zero temperature and their dependence on the physical distance between the static sources. We draw some conclusions about the validity domain of the dual superconductor picture.

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Dihadron production at the LHC: full next-to-leading BFKL calculation

The study of the inclusive production of a pair of charged light hadrons (a "dihadron" system) featuring high transverse momenta and well separated in rapidity represents a clear channel for the test of the BFKL dynamics at the Large Hadron Collider (LHC). This process has much in common with the well known Mueller-Navelet jet production; however, hadrons can be detected at much smaller values of the transverse momentum than jets, thus allowing to explore an additional kinematic range, supplementary to the one studied with Mueller-Navelet jets. Furthermore, it makes it possible to constrain not only the parton densities (PDFs) for the initial proton, but also the parton fragmentation functions (FFs) describing the detected hadron in the final state. Here, we present the first full NLA BFKL analysis for cross sections and azimuthal angle correlations for dihadrons produced in the LHC kinematic ranges. We make use of the Brodsky-Lapage-Mackenzie (BLM) optimization method to set the values of the renormalization scale and study the effect of choosing different values for the factorization scale. We also gauge the uncertainty coming from the use of different PDF and FF parametrizations.

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Dihadron Production at LHC: BFKL Predictions for Cross Sections and Azimuthal Correlations

A study of the inclusive production of a pair of hadrons (a "dihadron" system), having high transverse momenta and separated by a large interval of rapidity, is presented. This process has much in common with the widely discussed Mueller--Navelet jet production and can be also used to access the BFKL dynamics at proton colliders. Large contributions enhanced by logarithms of energy can be resummed in perturbation theory within the BFKL formalism in the next-to-leading logarithmic accuracy. The experimental study of dihadron production would provide with an additional clear channel to test the BFKL dynamics. The first theoretical predictions for cross sections and azimuthal angle correlations of the two hadrons produced with LHC kinematics are presented.

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High-Energy Resummation in Di-hadron Production at the LHC

We propose to study at the Large Hadron Collider (LHC) the inclusive production of a pair of hadrons (a "di-hadron" system) in a kinematics where two detected hadrons with high transverse momenta are separated by a large interval of rapidity. This process has much in common with the widely discussed Mueller-Navelet jet production and can also be used to access the dynamics of hard proton-parton interactions in the Regge limit. For both processes large contributions enhanced by logarithms of energy can be resummed in perturbation theory within the Balitsky-Fadin-Kuraev-Lipatov (BFKL) formalism with next-to-leading logarithmic accuracy (NLA). The experimental study of di-hadron production would provide with an additional clear channel to test the BFKL dynamics. We present here the first theoretical predictions for cross sections and azimuthal angle correlations of the di-hadrons produced with LHC kinematics.

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BFKL effects and central rapidity dependence in Mueller-Navelet jet production at 13 TeV LHC

A study of the production of Mueller-Navelet jets at 13 TeV LHC is presented, including BFKL resummation effects and investigating three different variants of the BLM scale optimization method. It is shown how the cross section and the azimuthal observables are affected by the exclusion of the events where, for a given rapidity interval between the two jets, one of these is produced in the central region.

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Flux tubes at finite temperature

The chromoelectric field generated by a static quark-antiquark pair, with its peculiar tube-like shape, can be nicely described, at zero temperature, within the dual superconductor scenario for the QCD confining vacuum. In this work we investigate, by lattice Monte Carlo simulations of the SU(3) pure gauge theory, the fate of chromoelectric flux tubes across the deconfinement transition. We find that, as the temperature is increased towards and above the deconfinement temperature $T_c$, the amplitude of the field inside the flux tube gets smaller, while the shape of the flux tube does not vary appreciably across deconfinement. This scenario with flux-tube "evaporation" above $T_c$ has no correspondence in ordinary (type-II) superconductivity, where instead the transition to the phase with normal conductivity is characterized by a divergent fattening of flux tubes as the transition temperature is approached from below. We present also some evidence about the existence of flux-tube structures in the magnetic sector of the theory in the deconfined phase.

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BKT phase transitions in two-dimensional non-Abelian spin models

It is argued that two-dimensional U(N) spin models for any N undergo a BKT-like phase transition, similarly to the famous XY model. This conclusion follows from the Berezinskii-like calculation of the two-point correlation function in U(N) models, approximate renormalization group analysis and numerical investigations of the U(2) model. It is shown, via Monte Carlo simulations, that the universality class of the U(2) model coincides with that of the XY model. Moreover, preliminary numerical results point out that two-dimensional SU(N) spin models with the fundamental and adjoint terms and N>4 exhibit two phase transitions of BKT type, similarly to Z(N) vector models.

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Mueller-Navelet jets at 13 TeV LHC: dependence on dynamic constraints in the central rapidity region

We study the production of Mueller-Navelet jets at 13 TeV LHC, within collinear factorization and including the BFKL resummation of energy logarithms in the next-to-leading approximation. We calculate several azimuthal correlations for different values of the rapidity separation $Y$ between the two jets and evaluate the effect of excluding those events where, for a given $Y$, one of the two jets is produced in the central region.

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