1,640 research outputs found
Holographic Oddballs
The spectrum of the glueball with is computed using different
bottom-up holographic models of QCD. The results indicate a lowest-lying state
lighter than in the determination by other methods, with mass
GeV. The in-medium properties of this gluonium are investigated, and stability
against thermal and density effects is compared to other hadronic systems.
Production and decay modes are identified, useful for searching the
glueball.Comment: 16 pages, 9 figures, 3 table
Nuclear Structure Functions at Low- in a Holographic Approach
Nuclear effects in deep inelastic scattering at low are
phenomenologically described changing the typical dynamical and/or kinematical
scales characterizing the free nucleon case. In a holographic approach, this
rescaling is an analytical property of the computed structure function
. This function is given by the sum of a conformal term and of a
contribution due to quark confinement, depending on IR hard-wall parameter
and on the mean square distances, related to a parameter ,
among quarks and gluons in the target. The holographic structure function per
nucleon in a nucleus is evaluated showing that a rescaling of the typical
nucleon size, and , due to nuclear binding, can be reabsorbed
in a -rescaling scheme. The difference between neutron and proton
structure functions and the effects of the longitudinal structure functions can
also be taken into account. The obtained theoretical results favourably compare
with the experimental data.Comment: 10 pages, 10 figure
On thermalization of a boost-invariant non Abelian plasma
Using a holographic method, we further investigate the relaxation towards the
hydrodynamic regime of a boost-invariant non-Abelian plasma taken
out-of-equilibrium. In the dual description, the system is driven
out-of-equilibrium by boundary sourcing, a deformation of the boundary metric,
as proposed by Chesler and Yaffe. The effects of several deformation profiles
on the bulk geometry are investigated by the analysis of the corresponding
solutions of the Einstein equations. The time of restoration of the
hydrodynamic regime is investigated: setting the effective temperature of the
system at the end of the boundary quenching to MeV, the
hydrodynamic regime is reached after a lapse of time of (1 fm/c).Comment: 24 pages, 11 figures. Improved numerical analysis, one more appendix,
two new figures. To appear in JHE
The Vector and Axial-Vector Charmonium-like States
After constructing all the tetraquark interpolating currents with
and in a systematic way, we
investigate the two-point correlation functions to extract the masses of the
charmonium-like states with QCD sum rule. For the
charmonium-like state, GeV, which implies a possible
tetraquark interpretation for the state Y(4660). The masses for both the
and charmonium-like states are
around GeV, which are slightly above the mass of X(3872). For the
charmonium-like state, the extracted mass is GeV. We also discuss the possible decay modes and experimental search of
the charmonium-like states.Comment: 18 pages, 6 figures and 6 table
Quarkonium dissociation in a far-from-equilibrium holographic setup
The real-time dissociation of the heavy quarkonium in a strongly coupled
boost-invariant non-Abelian plasma relaxing towards equilibrium is analyzed in
a holographic framework. The effects driving the plasma out of equilibrium are
described by boundary quenching, impulsive variations of the boundary metric.
Quarkonium is represented by a classical string with endpoints kept close to
the boundary. The evolution of the string profile is computed in the
time-dependent geometry, and the dissociation time is evaluated for different
configurations with respect to the direction of the plasma expansion.
Dissociation occurs fastly for the quarkonium placed in the transverse plane.Comment: 14 pages, 8 figures. References added. Matches the published versio
Vertical dipoles to detect self potential signals in a seismic area of southern Italy: Tito station
International audienceSince 2000 the Institute of Methodologies for the Environmental Analysis (National Council of Research, Tito, Italy) installed a geophysical monitoring network able to detect geoelectric, geochemic and seismometric parameters in seismic areas of southern Italy. During this period a very large data-base of geophysical time series has been organized and it is actually available to assess robust statistical methodologies to identify geophysical anomalous patterns linked with local seismicity. To better understand the influence of rain and cultural noise on geoelectrical signals (Self Potential), during May 2004 we drilled in Tito station a 20 m-depth hole to measure the SP vertical component. The array is characterized by five Pb-PbCl2 electrodes put at different depths. The common electrode is fixed at 20 m. In this work we present some electrical anomalies probably correlated with local seismic activity on vertical dipoles recorded in Tito station
Multifractal variability in geoelectrical signals and correlations with seismicity: a study case in southern Italy
International audienceMultifractal fluctuations in the time dynamics of geoelectrical data, recorded in a seismic area of southern Italy, have been revealed using the Multifractal Detrended Fluctuation Analysis (MF-DFA), which allows to detect multifractality in nonstationary signals. Our findings show that the geoelectrical time series, recorded in the seismic area of southern Apennine Chain (Italy), is multifractal. The time evolution of the multifractality suggests that the multifractal degree increases prior the occurrence of earthquakes. This study aims to propose another approach to investigate the complex dynamics of earthquake-related geoelectrical signals
Strong Interactions at Low Energy
The lectures review some of the basic concepts relevant for an understanding
of the low energy properties of the strong interactions: chiral symmetry,
spontaneous symmetry breakdown, Goldstone bosons, quark condensate. The
effective field theory used to analyze the low energy structure is briefly
sketched. As an illustration, I discuss the implications of the recent data on
the decay for the magnitude of the quark condensate.Comment: Lectures given at the school of physics "Understanding the structure
of hadrons", Prague, July 2001, 20 p
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