345 research outputs found
Yano-Koonin-Podgoretskii Parametrisation of the Hanbury Brown-Twiss Correlator
The Yano-Koonin-Podgoretskii (YKP) parametrisation of Hanbury Brown-Twiss
(HBT) two-particle correlation functions opens new strategies for extracting
the emission duration and testing the longitudinal expansion in heavy-ion
collisions. Based on the recently derived model-independent expressions, we
present a detailed parameter study of the YKP parameters for a finite,
hydrodynamically expanding source model of heavy-ion collisions. For the class
of models studied here, we show that the three YKP radius parameters have an
interpretation as longitudinal extension, transverse extension and emission
duration of the source in the YKP frame. This frame is specified by the fourth
fit parameter, the Yano-Koonin velocity which describes to a good approximation
the velocity of the fluid element with highest emissivity and allows to test
for the longitudinal expansion of the source. Deviations from this
interpretation of the YKP parameters are discussed quantitatively.Comment: 38 pages, REVTeX, 11 PS-figures, to be published in Z.Phys.
The ossification of the metacarpal and phalangeal bones in human foetuses
An evaluation was made of the ossification level of the metacarpal and phalangeal
bones in human foetuses of both sexes from the 4th to the 9th month of
gestation. Our results indicate that ossification of phalangeal bones 1 to 5 always
started at the distal end of the phalanx and endochondral ossification
prevailed in the proximal phalanx of the thumb
Space-time Characteristics of the Fireball from HBT Interferometry
We present the Yano-Koonin-Podgoretskii parametrisation of the correlation
function. Compared to the conventionally used Cartesian parametrisation, this
one provides more straightforward measurement of the duration of the emission
process in the fireball and a clearer signal of the longitudinal expansion,
which is expected in ulrarelativistic heavy ion collisions.Comment: 13 pages LaTeX,3 figures incl. with epsf-style. Proceedings of "Heavy
Ion Workshop on Particle Physics", Sept. 2.-6., 1996, Bratislava, Slovakia,
misprint in Eq.(27) correcte
Intensity interferometry of thermal photons from relativistic heavy ion collisions
Intensity interferometry of thermal photons, having transverse momenta 0.1 -- 2.0 GeV, produced in relativistic collision of heavy nuclei is
studied. It is seen to provide an accurate information about the temporal and
spatial structure of the interacting system. The source dimensions and their
dependence revealed by the photon interferometry, display a richness not
seen in pion interferometry. We attribute this to difference in the source
functions, the fact that photons come out from every stage of the collision and
from every point in the system, and the fact that the rate of production of
photons is different for the quark-gluon plasma, which dominates the early hot
stage, and the hadronic matter which populates the last phase of the collision
dynamics. The usefulness of this procedure is demonstrated by an application to
collision of lead nuclei at the CERN SPS. Prediction for the transverse
momentum dependence of the sizes for SPS, RHIC, and LHC energies are given.Comment: 16 pages, 11 figures. Added discussions and references. To appear in
Phys. Rev.
The Renyi entropy H_2 as a rigorous, measurable lower bound for the entropy of the interaction region in multiparticle production processes
A model-independent lower bound on the entropy S of the multiparticle system
produced in high energy collisions, provided by the Renyi entropy H_2, is shown
to be very effective. Estimates show that the ratio H_2/S remains close to one
half for all realistic values of the parameters.Comment: Eur. Phys. J. C in print, 17 pages, 5 figure
Correspondence between HBT radii and the emission zone in non-central heavy ion collisions
In non-central collisions between ultra-relativistic heavy ions, the
freeze-out distribution is anisotropic, and its major longitudinal axis may be
tilted away from the beam direction. The shape and orientation of this
distribution are particularly interesting, as they provide a snapshot of the
evolving source and reflect the space-time aspect of anisotropic flow.
Experimentally, this information is extracted by measuring pion HBT radii as a
function of angle with respect to the reaction plane. Existing formulae
relating the oscillations of the radii and the freezeout anisotropy are in
principle only valid for Gaussian sources with no collective flow. With a
realistic transport model of the collision, which generates flow and
non-Gaussian sources, we find that these formulae approximately reflect the
anisotropy of the freezeout distribution.Comment: 9 pages, 8 figure
Transport model analysis of particle correlations in relativistic heavy ion collisions at femtometer scales
The pion source as seen through HBT correlations at RHIC energies is
investigated within the UrQMD approach. We find that the calculated transverse
momentum, centrality, and system size dependence of the Pratt-HBT radii
and are reasonably well in line with experimental data. The predicted
values in central heavy ion collisions are larger as compared to
experimental data. The corresponding quantity of the
pion emission source is somewhat larger than experimental estimates.Comment: 12 pages, 5 figures, to be published in PR
Quantum Opacity, the RHIC HBT Puzzle, and the Chiral Phase Transition
We present a relativistic quantum mechanical treatment of opacity and
refractive effects that allows reproduction of observables measured in two-pion
(HBT) interferometry and pion spectra at RHIC. The inferred emission duration
is substantial. The results are consistent with the emission of pions from a
system that has a restored chiral symmetry.Comment: 4 pages, 2 figures. This version mentions shows the STAR 200 GeV
data, and includes some technical improvements. The agreement with experiment
is improved slightly, and the parameters of the model are changed slightl
- …