2,825 research outputs found
Heavy quark(onium) at LHC: the statistical hadronization case
We discuss the production of charmonium in nuclear collisions within the
framework of the statistical hadronization model. We demonstrate that the model
reproduces very well the availble data at RHIC. We provide predictions for the
LHC energy where, dependently on the charm production cross section, a
dramatically different behaviour of charmonium production as a function of
centrality might be expected. We discuss also the case in elementary
collisions, where clearly the statistical model does not reproduce the
measurements.Comment: 8 pages, 5 figures; proceeding of SQM09, Buzios, Brazil, to be
published in J. Phys.
Has the Quark-Gluon Plasma been seen?
Data from the first three years of running at RHIC are reviewed and put into
context with data obtained previously at the AGS and SPS and with the physics
question of creation of a quark-gluon plasma in high energy heavy ion
collisions. Also some very recent and still preliminary data from run4 are
included.Comment: plenary paper, Lepton-Photon 2005, Uppsala, Swede
Hadron production in Au-Au collisions at RHIC
We present an analysis of particle production yields measured in central
Au-Au collisions at RHIC in the framework of the statistical thermal model. We
demonstrate that the model extrapolated from previous analyses at SPS and AGS
energy is in good agreement with the available experimental data at GeV implying a high degree of chemical equilibration. Performing a
fit to the data, the range of thermal parameters at chemical freezeout
is determined. At present, the best agreement of the model and the data is
obtained with the baryon chemical potential MeV and
temperature MeV. More ratios, such as multistrange baryon to
meson, would be required to further constrain the chemical freezeout
conditions. Extrapolating thermal parameters to higher energy, the predictions
of the model for particle production in Au-Au reactions at GeV
are also given.Comment: Final version, minor changes to text and figures. To appear in Phys.
Lett.
Tuning of structure inversion asymmetry by the -doping position in (001)-grown GaAs quantum wells
Structure and bulk inversion asymmetry in doped (001)-grown GaAs quantum
wells is investigated by applying the magnetic field induced photogalvanic
effect. We demonstrate that the structure inversion asymmetry (SIA) can be
tailored by variation of the delta-doping layer position. Symmetrically-doped
structures exhibit a substantial SIA due to impurity segregation during the
growth process. Tuning the SIA by the delta-doping position we grow samples
with almost equal degrees of structure and bulk inversion asymmetry.Comment: 4 pages 2 figure
Measurement of the space-time interval between two events using the retarded and advanced times of each event with respect to a time-like world-line
Several recent studies have been devoted to investigating the limitations
that ordinary quantum mechanics and/or quantum gravity might impose on the
measurability of space-time observables. These analyses are often confined to
the simplified context of two-dimensional flat space-time and rely on a simple
procedure for the measurement of space-like distances based on the exchange of
light signals. We present a generalization of this measurement procedure
applicable to all three types of space-time intervals between two events in
space-times of any number of dimensions. We also present some preliminary
observations on an alternative measurement procedure that can be applied taking
into account the gravitational field of the measuring apparatus, and briefly
discuss quantum limitations of measurability in this context.Comment: 17 page
Gravitational strings. Do we see one?
I present a class of objects called gravitational strings (GS) for their
similarity to the conventional cosmic strings: even though the former are just
singularities in flat spacetime, both varieties are equally "realistic", they
may play equally important cosmological r\^ole and their lensing properties are
akin. I argue that the enigmatic object CSL-1 is an evidence in favor of the
existence of GS.Comment: The published version. Minor correction
Lambda(1520) production in d+Au collisions at RHIC
Recent results of (1520) resonance production in d+Au collisions at
200 GeV are presented and discussed in terms of the
evolution and freeze-out conditions of a hot and dense fireball medium. Yields
and spectra are compared to results from p+p and Au+Au collisions. The
(1520)/ ratio in d+Au collisions ratio is consistent with the
ratio in p+p collisions. This suggests a short time for elastic interactions
between chemical and thermal freeze-out. One can conclude that the interaction
volume in d+Au collisions is small.Comment: 4 Pages, 3 figures, conference proceedings Quark Matter 200
Vacuum energy: quantum hydrodynamics vs quantum gravity
We compare quantum hydrodynamics and quantum gravity. They share many common
features. In particular, both have quadratic divergences, and both lead to the
problem of the vacuum energy, which in the quantum gravity transforms to the
cosmological constant problem. We show that in quantum liquids the vacuum
energy density is not determined by the quantum zero-point energy of the phonon
modes. The energy density of the vacuum is much smaller and is determined by
the classical macroscopic parameters of the liquid including the radius of the
liquid droplet. In the same manner the cosmological constant is not determined
by the zero-point energy of quantum fields. It is much smaller and is
determined by the classical macroscopic parameters of the Universe dynamics:
the Hubble radius, the Newton constant and the energy density of matter. The
same may hold for the Higgs mass problem: the quadratically divergent quantum
correction to the Higgs potential mass term is also cancelled by the
microscopic (trans-Planckian) degrees of freedom due to thermodynamic stability
of the whole quantum vacuum.Comment: 14 pages, no figures, added section on the problem of Higgs mass,
version accepted for the special issue of JETP Letter
Complex Wave Numbers in the Vicinity of the Schwarzschild Event Horizon
This paper is devoted to investigate the cold plasma wave properties outside
the event horizon of the Schwarzschild planar analogue. The dispersion
relations are obtained from the corresponding Fourier analyzed equations for
non-rotating and rotating, non-magnetized and magnetized backgrounds. These
dispersion relations provide complex wave numbers. The wave numbers are shown
in graphs to discuss the nature and behavior of waves and the properties of
plasma lying in the vicinity of the Schwarzschild event horizon.Comment: 21 pages, 9 figures, accepted for publication Int. J. Mod. Phys.
Transverse energy per charged particle at relativistic energies from a statistical model with expansion
Transverse energy and charged particle pseudorapidity densities at
midrapidity and their ratio, ,
are evaluated in a statistical model with longitudinal and transverse flows for
the wide range of colliders, from AGS to RHIC at GeV.
Evaluations are done at freeze-out parameters established independently from
fits to observed particle yields and spectra. Decays of hadron
resonances are treated thoroughly and are included in derivations of
and . The predictions of the model
agree well with the experimental data. However, some (explicable)
overestimation of the ratio has been observed.Comment: Revtex, 11 pages, 1 figure (included), The revised version with the
title changed and new conclusions added, to appear in Eur. Phys. J.
- …