2,007 research outputs found
Particle Number Fluctuations in Canonical Ensemble
Fluctuations of charged particle number are studied in the canonical
ensemble. In the infinite volume limit the fluctuations in the canonical
ensemble are different from the fluctuations in the grand canonical one. Thus,
the well-known equivalence of both ensembles for the average quantities does
not extend for the fluctuations. In view of a possible relevance of the results
for the analysis of fluctuations in nuclear collisions at high energies, a role
of the limited kinematical acceptance is studied.Comment: 13 pages, 9 figures, LaTe
Kinetic equation with exact charge conservation
We formulate the kinetic master equation describing the production of charged
particles which are created or destroyed only in pairs due to the conservation
of their Abelian charge.Our equation applies to arbitrary particle
multiplicities and reproduces the equilibrium results for both canonical (rare
particles) and grand canonical (abundant particles) systems. For canonical
systems, the equilibrium multiplicity is much lower and the relaxation time is
much shorter than the naive extrapolation from the grand canonical ensemble
results. Implications for particle chemical equilibration in heavy-ion
collisions are discussed.Comment: 4 Pages in RevTe
Fluctuations, strangeness and quasi-quarks in heavy-ion collisions from lattice QCD
We report measurements of diagonal susceptibilities for the baryon number,
chi_B, electrical charge, chi_Q, third component of isospin, chi_I,
strangeness, chi_S, and hypercharge, chi_Y, as well as the off-diagonal chi_BQ,
chi_BY, chi_BS, etc. We show that the ratios of susceptibilities in the high
temperature phase are robust variables, independent of lattice spacing, and
therefore give predictions for experiments. We also investigate strangeness
production and flavour symmetry breaking matrix elements at finite temperature.
Finally, we present evidence that in the high temperature phase of QCD the
different flavour quantum numbers are excited in linkages which are exactly the
same as one expects from quarks. We present some investigations of these
quark-like quasi particles
Highlights of the Beam Energy Scan from STAR
The first part of the beam energy scan (BES) program at RHIC was successfully
completed in the years 2010 and 2011. First STAR results from particle yield
measurements are in good agreement with previously published data from SPS and
AGS experiments whereas other results like azimuthal HBT and
event-by-event fluctuations differ at some energies. In addition, new
observations like the centrality dependence of chemical freeze-out parameters
( and ) or the smoothly increasing difference with
decreasing energy in the elliptic flow between particles and
corresponding anti-particles, are discussed.Comment: CPOD 2011 proceedings, 5 pages, 4 figure
Dynamical interpretation of chemical freeze-out in heavy ion collisions
It is demonstrated that there exists a direct correlation between chemical
freeze-out point and the softest point of the equation of state where the
pressure divided by the energy density, , has a minimum.
A dynamical model is given as an example where the passage of the softest point
coincides with the condition for chemical freeze-out, namely an average energy
per hadron 1 GeV. The sensitivity of the result to the equation of
state used is discussed.Comment: 10 pages, 2 figure
The Tsallis Distribution in Proton-Proton Collisions at = 0.9 TeV at the LHC
The Tsallis distribution has been used recently to fit the transverse
momentum distributions of identified particles by the STAR and PHENIX
collaborations at the Relativistic Heavy Ion Collider and by the ALICE and CMS
collaborations at the Large Hadron Collider. Theoretical issues are clarified
concerning the thermodynamic consistency of the Tsallis distribution in the
particular case of relativistic high energy quantum distributions. An improved
form is proposed for describing the transverse momentum distribution and fits
are presented together with estimates of the parameter and the temperature
.Comment: 15 pages, 7 figures. arXiv admin note: substantial text overlap with
arXiv:1106.340
Non-extensivity of the QCD pT spectra
We try to establish a connection between the hadronic distributions, in
proton-proton collisions at very high transverse momentum ,
obtained via perturbative QCD and the Tsallis non extensive statistics. Our
motivation is that while the former is expected to be valid at extremely high
momentum, due to asymptotic freedom, the latter has been very successful in
describing experimental spectra over a wide range of momentum. Matching the non
extensive statistics with the asymptotic behaviour expected
from QCD leads to the value of .Comment: 4 page
- …