1,619 research outputs found
The Interacting Gluon Model: a review
The Interacting Gluon Model (IGM) is a tool designed to study energy flow,
especially stopping and leading particle spectra, in high energy hadronic
collisions. In this model, valence quarks fly through and the gluon clouds of
the hadrons interact strongly both in the soft and in the semihard regime.
Developing this picture we arrive at a simple description of energy loss, given
in terms of few parameters, which accounts for a wide variety of experimental
data. This text is a survey of our main results and predictions.Comment: 22 pages, 21 figure
Spectroscopy of the All-Charm Tetraquark
We use a non-relativistic model to study the mass spectroscopy of a
tetraquark composed by quarks in the
diquark-antidiquark picture. By numerically solving the Schr\"{o}dinger
equation with a Cornell-inspired potential, we separate the four-body problem
into three two-body problems. Spin-dependent terms (spin-spin, spin-orbit and
tensor) are used to describe the splitting structure of the spectrum
and are also extended to the interaction between diquarks. Recent experimental
data on charmonium states are used to fix the parameters of the model and a
satisfactory description of the spectrum is obtained. We find that the
spin-dependent interaction is sizable in the diquark-antidiquark system,
despite of the heavy diquark mass, and that the diquark has a finite size if
treated in analogy to the systems. We find that the lowest -wave
tetraquarks might be below their thresholds of spontaneous
dissociation into low-lying charmonium pairs, while orbital and radial
excitations would be mostly above the corresponding charmonium pair threshold.
These states could be investigated in the forthcoming experiments at LHCb and
Belle II.Comment: Presented at the XVII International Conference on Hadron Spectroscopy
and Structure - Hadron2017, 25-29 September, 2017, University of Salamanca,
Salamanca, Spai
Hadronic form factors and the secondary production cross section: an update
Improving previous calculations, we compute the cross section using the most complete effective lagrangians available. The
new crucial ingredients are the form factors on the charm meson vertices, which
are determined from QCD sum rules calculations. Some of them became available
only very recently and the last one, needed for our present purpose, is
calculated in this work.Comment: 12 pages, 9 eps figure
Looking for meson molecules in B decays
We discuss the possibility of observing a loosely bound molecular state in a
B three-body hadronic decay. In particular we use the QCD sum rule approach to
study a molecular current. We consider an isovector-scalar
molecular current and we use the two-point and
three-point functions to study the mass and decay width of such state. We
consider the contributions of condensates up to dimension six and we work at
leading order in . We obtain a mass around 1.1 GeV, consistent with a
loosely bound state, and a decay width
around 10 MeV.Comment: 7 pages, 8 figure
Does the production asymmetry decrease at large ?
We have applied the meson cloud model (MCM) to calculate the asymmetries in
and meson production in high energy -nucleus and
-nucleus collisions. We find a good agreement with recent data. Our
results suggest that the asymmetries may decrease at large .Comment: revised version with new figures and added references to appear in
Phys. Rev. Let
Gluon saturation and Feynman scaling in leading neutron production
In this paper we extend the color dipole formalism to the study of leading
neutron production in collisions at high energies
and estimate the related observables, which were measured at HERA and may be
analysed in future electron-proton () colliders. In particular, we
calculate the Feynman distribution of leading neutrons, which is
expressed in terms of the pion flux and the photon-pion total cross section. In
the color dipole formalism, the photon-pion cross section is described in terms
of the dipole-pion scattering amplitude, which contains information about the
QCD dynamics at high energies and gluon saturation effects. We consider
different models for the scattering amplitude, which have been used to describe
the inclusive and diffractive HERA data. Moreover, the model dependence of
our predictions with the description of the pion flux is analysed in detail. We
show that the recently released H1 leading neutron spectra can be reproduced
using the color dipole formalism and that these spectra could help us to
observe more clearly gluon saturation effects in future colliders.Comment: 10 pages, 5 figure
Nonextensive hydrodynamics for relativistic heavy-ion collisions
The nonextensive one-dimensional version of a hydrodynamical model for
multiparticle production processes is proposed and discussed. It is based on
nonextensive statistics assumed in the form proposed by Tsallis and
characterized by a nonextensivity parameter . In this formulation the
parameter characterizes some specific form of local equilibrium which is
characteristic for the nonextensive thermodynamics and which replaces the usual
local thermal equilibrium assumption of the usual hydrodynamical models. We
argue that there is correspondence between the perfect nonextensive
hydrodynamics and the usual dissipative hydrodynamics. It leads to simple
expression for dissipative entropy current and allows for predictions for the
ratio of bulk and shear viscosities to entropy density, and ,
to be made.Comment: Final version accepted for publication in Phys. Rev.
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