1,559 research outputs found
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
Covariant statistical mechanics and the stress-energy tensor
After recapitulating the covariant formalism of equilibrium statistical
mechanics in special relativity and extending it to the case of a non-vanishing
spin tensor, we show that the relativistic stress-energy tensor at
thermodynamical equilibrium can be obtained from a functional derivative of the
partition function with respect to the inverse temperature four-vector \beta.
For usual thermodynamical equilibrium, the stress-energy tensor turns out to be
the derivative of the relativistic thermodynamic potential current with respect
to the four-vector \beta, i.e. T^{\mu \nu} = - \partial \Phi^\mu/\partial
\beta_\nu. This formula establishes a relation between stress-energy tensor and
entropy current at equilibrium possibly extendable to non-equilibrium
hydrodynamics.Comment: 4 pages. Final version accepted for publication in Phys. Rev. Let
Global hyperon polarization at local thermodynamic equilibrium with vorticity, magnetic field and feed-down
The system created in ultrarelativistic nuclear collisions is known to behave
as an almost ideal liquid. In non-central collisions, due to the large orbital
momentum, such a system might be the fluid with the highest vorticity ever
created under laboratory conditions. Particles emerging from such a highly
vorticous fluid are expected to be globally polarized with their spins on
average pointing along the system angular momentum. Vorticity-induced
polarization is the same for particles and antiparticles, but the intense
magnetic field generated in these collisions may lead to the splitting in
polarization. In this paper we outline the thermal approach to the calculation
of the global polarization phenomenon for particles with spin and we discuss
the details of the experimental study of this phenomenon, estimating the effect
of feed-down. A general formula is derived for the polarization transfer in
two-body decays and, particularly, for strong and electromagnetic decays. We
find that accounting for such effects is crucial when extracting vorticity and
magnetic field from the experimental data.Comment: 14 pages, 1 figure. Final version published in PRC with one more
formula and slightly revised tex
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
Extreme Energy nu_tau Propagation Through the Earth
The propagation of extremely energetic nu_tau's through the Earth is studied
by means of a detailed Monte Carlo simulation. All major mechanisms of nu_tau
interactions and tau energy loss as well as all its relevant decay modes are
properly taken into account. The detection possibility of nu_tau's emerging
from Earth in forthcoming neutrino telescopes is addressedComment: Revised version, to be published in Astroparticle Physic
The Hagedorn Temperature and Partition Thermodynamics
We review the resonance gas formalism of hadron thermodynamics and recall
that an exponential increase of the resonance spectrum leads to a limiting
temperature of hadronic matter. We then show that the number p(n) of ordered
partitions of an integer n grows exponentially with n and satisfies the integer
counterpart of the statistical bootstrap equation. Considering the set of all
partitions as a Gibbs ensemble provides a partition thermodynamics which is
also governed by a limiting temperature, determined by the combinatorial
structure of the problem. Further associating intrinsic quantum numbers to
integers results in a phase diagram equivalent to that found in QCD for
hadronic matter as function of temperature and baryochemical potential.Comment: Dedicated to Rolf Hagedorn, 1919-2003. 11 pages, 3 figures. Final
version accepted for publication in the European Physical Journal
Possible Resolutions of the D-Paradox
We propose possible ways of explaining the net charge event-by-event
fluctuations in Au+Au collisions at the Relativistic Heavy Ion Collider within
a quark recombination model. We discuss various methods of estimating the
number of quarks at recombination and their implications for the predicted net
charge fluctuations. We also discuss the possibility of diquark and
quark-antiquark clustering above the deconfinement temperature.Comment: 5 pages, 2 figure
Xi and AntiXi production in Pb+Pb collisions at 40 AGeV at CERN SPS
First results on the production of Xi and AntiXi hyperons in Pb+Pb
interactions at 40 AGeV are presented. The AntiXi/Xi ratio at midrapidity is
studied as a function of collision centrality. The ratio shows no significant
centrality dependence within statistical errors; it ranges from 0.07 to 0.15.
The AntiXi/Xi ratio for central Pb+Pb collisions increases strongly with the
collision energy.Comment: 6 pages, 6 figures, proceedings of SQM03, to be published in Journal
of Physics G; V2: changes in table 1 and figure
THERMUS -- A Thermal Model Package for ROOT
THERMUS is a package of C++ classes and functions allowing
statistical-thermal model analyses of particle production in relativistic
heavy-ion collisions to be performed within the ROOT framework of analysis.
Calculations are possible within three statistical ensembles; a grand-canonical
treatment of the conserved charges B, S and Q, a fully canonical treatment of
the conserved charges, and a mixed-canonical ensemble combining a canonical
treatment of strangeness with a grand-canonical treatment of baryon number and
electric charge. THERMUS allows for the assignment of decay chains and detector
efficiencies specific to each particle yield, which enables sensible fitting of
model parameters to experimental data.Comment: to be published in Computer Physics Communication
System Size Dependence of Particle Production at the SPS
Recent results on the system size dependence of net-baryon and hyperon
production as measured at the CERN SPS are discussed. The observed Npart
dependences of yields, but also of dynamical properties, such as average
transverse momenta, can be described in the context of the core corona
approach. Other observables, such as antiproton yields and net-protons at
forward rapidities, do not follow the predictions of this model. Possible
implications for a search for a critical point in the QCD phase diagram are
discussed. Event-by-event fluctuations of the relative core to corona source
contributions might influence fluctuation observables (e.g. multiplicity
fluctuations). The magnitude of this effect is investigated.Comment: 10 pages, 4 figurs. Proceedings of the 6th International Workshop on
Critical Point and Onset of Deconfinement in Dubna, Aug. 201
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