418 research outputs found
Statistical hadronization and hadronic microcanonical ensemble I
We present a full treatment of the microcanonical ensemble of the ideal
hadron-resonance gas in a quantum-mechanical framework which is appropriate for
the statistical model of hadronization. By using a suitable transition operator
for hadronization we are able to recover the results of the statistical theory,
particularly the expressions of the rates of different channels. Explicit
formulae are obtained for the phase space volume or density of states of the
ideal relativistic gas in quantum statistics which, for large volumes, turn to
a cluster decomposition whose terms beyond the leading one account for
Bose-Einstein and Fermi-Dirac correlations. The problem of the computation of
the microcanonical ensemble and its comparison with the canonical one, which
will be the main subject of a forthcoming paper, is addressed.Comment: 15 pages, LaTeX macros svjour.cls and svepj.clo needed, revised
version to be published in Eur. Phys. J.
The microcanonical ensemble of the ideal relativistic quantum gas with angular momentum conservation
We derive the microcanonical partition function of the ideal relativistic
quantum gas with fixed intrinsic angular momentum as an expansion over fixed
multiplicities. We developed a group theoretical approach by generalizing known
projection techniques to the Poincare' group. Our calculation is carried out in
a quantum field framework and applies to particles with any spin. It extends
known results in literature in that it does not introduce any large volume
approximation and it takes particle spin fully into account. We provide
expressions of the microcanonical partition function at fixed multiplicities in
the limiting classical case of large volumes and large angular momenta and in
the grand-canonical ensemble. We also derive the microcanonical partition
function of the ideal relativistic quantum gas with fixed parity.Comment: 38 pages; minor corrections to the formulae for the published versio
Crossover transition in bag-like models
We formulate a simple model for a gas of extended hadrons at zero chemical
potential by taking inspiration from the compressible bag model. We show that a
crossover transition qualitatively similar to lattice QCD can be reproduced by
such a system by including some appropriate additional dynamics. Under certain
conditions, at high temperature, the system consist of a finite number of
infinitely extended bags, which occupy the entire space. In this situation the
system behaves as an ideal gas of quarks and gluons.Comment: Corresponds to the published version. Added few references and
changed the titl
Particle Number Fluctuations in Statistical Model with Exact Charge Conservation Laws
Even though the first momenta i.e. the ensemble average quantities in
canonical ensemble (CE) give the grand canonical (GC) results in large
multiplicity limit, the fluctuations involving second moments do not respect
this asymptotic behaviour. Instead, the asymptotics are strikingly different,
giving a new handle in study of statistical particle number fluctuations in
relativistic nuclear reactions. Here we study the analytical large volume
asymptotics to general case of multispecies hadron gas carrying fixed baryon
number, strangeness and electric charge. By means of Monte Carlo simulations we
have also studied the general multiplicity probability distributions taking
into account the decay chains of resonance states.Comment: 4 pages, 2 figures. The report of the talk given in Strangeness in
Quark Matter 2004, Cape Town. Submitted to J. Phys. G: Nucl. Part. Phy
A Monte-Carlo generator for statistical hadronization in high energy e+e- collisions
We present a Monte-Carlo implementation of the Statistical Hadronization
Model in e+e- collisions. The physical scheme is based on the statistical
hadronization of massive clusters produced by the event generator Herwig within
the microcanonical ensemble. We present a preliminary comparison of several
observables with measurements in e+e- collisions at the Z peak. Although a fine
tuning of the model parameters is not carried out, a general good agreement
between its predictions and data is found.Comment: 19 pages, 28 figures, 6 tables. v2: added sections on comparison
between the Statistical Hadronization Model and the Cluster Model and on the
interplay between Herwig cluster splitting algorithm and Statistical
Hadronization Model predictions. Fixed typos and references added. Version
accepted for publication in EPJ
Statistical hadronization with exclusive channels in e+e- annihilation
We perform a systematic analysis of exclusive hadronic channels in e+e-
collisions at centre-of-mass energies between 2.1 and 2.6 GeV within the
statistical hadronization model. Because of the low multiplicities involved,
calculations have been carried out in the full microcanonical ensemble,
including conservation of energy-momentum, angular momentum, parity, isospin,
and all relevant charges. We show that the data is in an overall good agreement
with the model for an energy density of about 0.5 GeV/fm^3 and an extra
strangeness suppression parameter gamma_S ~ 0.7, essentially the same values
found with fits to inclusive multiplicities at higher energy.Comment: 27 pages, 12 figure
Isospin and isospin/strangeness correlations in relativistic heavy ion collisions
A fundamental symmetry of nuclear and particle physics is isospin whose third
component is the Gell-Mann/Nishijima expression I(z)=Q-(B+S)/2 . The role of
isospin symmetry in relativistic heavy ion collisions is studied. An isospin
I(z), strangeness S correlation is shown to be a direct and simple measure of
flavor correlations, vanishing in a Qg phase of uncorrelated flavors in both
symmetric N=Z and asymmetric N not equal to Z systems. By contrast, in a hadron
phase, a I(z)/S correlation exists as long as the electrostatic charge chemical
potential mu(Q)does not equal 0 as in N not equal to Z asymmetric systems. A
parallel is drawn with a Zeeman effect which breaks a spin degeneracyComment: 11 page
Relativistic Nucleus-Nucleus Collisions: from the BEVALAC to RHIC
I briefly describe the initial goals of relativistic nuclear collisions
research, focusing on the LBL Bevatron/Bevalac facility in the 1970's. An early
concept of high hadronic density fireball formation, and subsequent isentropic
decay (preserving information as to the high density stage) led to an outline
of physics observables that could determine the nuclear matter equation of
state at several times nuclear ground state matter density. With the advent of
QCD the goal of locating, and characterizing the hadron-parton deconfinement
phase transformation suggested the need for higher , the research
thus moving to the BNL AGS and CERN SPS, finally to RHIC at BNL. A set of
physics observables is discussed where present data span the entire
domain, from Bevalac and SIS at GSI, to top RHIC energy. Referring,
selectively, to data concerning bulk hadron production, the overall
evolution of directed and radial flow observables, and of pion pair
Bose-Einstein correlation are discussed. The hadronization process is studied
in the grand canonical statistical model. The resulting hadronization points in
the plane T vs. converge onto the parton-hadron phase boundary
predicted by finite lattice QCD, from top SPS to RHIC energy. At lower
SPS and top AGS energy a steep strangeness maximum occurs at which the
Wroblewski parameter 0.6; a possible connection to the QCD
critical point is discussed. Finally the unique new RHIC physics is addressed:
high hadron suppression and jet "tomography".Comment: 19 pages, 11 figure
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