5,815 research outputs found
Squeezed K^+ K^- correlations in high energy heavy ion collisions
The hot and dense medium formed in high energy heavy ion collisions may
modify some hadronic properties. In particular, if hadron masses are shifted
in-medium, it was demonstrated that this could lead to back-to-back squeezed
correlations (BBC) of particle-antiparticle pairs. Although well-established
theoretically, the squeezed correlations have not yet been discovered
experimentally. A method has been suggested for the empirical search of this
effect, which was previously illustrated for phi-phi pairs. We apply here the
formalism and the suggested method to the case of K^+ K^- pairs, since they may
be easier to identify experimentally. The time distribution of the emission
process plays a crucial role in the survival of the BBC's. We analyze the cases
where the emission is supposed to occur suddenly or via a Lorentzian
distribution, and compare with the case of a Levy distribution in time. Effects
of squeezing on the correlation function of identical particles are also
analyzed.Comment: 9 pages and 6 figures (figures 2 to 6 contain 4 plots each).
Paragraph added to text, figures 2 to 6 revised for improving visualizatio
Squeezed correlations of strange particle-antiparticles
Squeezed correlations of hadron-antihadron pairs are predicted to appear if
their masses are modified in the hot and dense medium formed in high energy
heavy ion collisions. If discovered experimentally, they would be an
unequivocal evidence of in-medium mass shift found by means of hadronic probes.
We discuss a method proposed to search for this novel type of correlation,
illustrating it by means of D_s-mesons with in-medium shifted masses. These
particles are expected to be more easily detected and identified in future
upgrades at RHIC.Comment: 6 pages, 3 figures with parts a) and b), SQM 2009 contribution; added
acknowledgmen
HBT Interferometry: Historical Perspective
I review the history of HBT interferometry, since its discovery in the mid
1950's, up to the recent developments and results from BNL/RHIC experiments. I
focus the discussion on the contributions to the subject given by members of
our Brazilian group.Comment: 32 pages, 42 figures; corrected typos, replaced corrupted figure
Disappearance of Squeezed Back-to-Back Correlations - a new signal of hadron freeze-out from a supercooled Quark Gluon Plasma
We briefly discuss four different possible types of transitions from quark to
hadronic matter and their characteristic signatures in terms of correlations.
We also highlight the effects arising from mass modification of hadrons in hot
and dense hadronic matter, as well as their quantum statistical consequences:
the appearance of squeezed quantum states and the associated experimental
signatures, i.e., the back-to-back correlations of particle - anti-particle
pairs. We briefly review the theoretical results of these squeezed quanta,
generated by in-medium modified masses, starting from the first indication of
the existence of surprising particle - anti-particle correlations, and ending
by considering the effects of chiral dynamics on these correlation patterns. A
prerequisite for such a signature is the experimental verification that these
theoretically predicted back-to-back correlation of particle anti-particle
pairs are, in fact, observable in high energy heavy ion reactions. Therefore,
the experimental observation of back-to-back correlations in high energy heavy
ion reactions would be a unique signature, proving the existence of in-medium
mass modification of hadronic states. On the other hand, their disappearance at
some threshold centrality or collision energy would indicate that the hadron
formation mechanism would have qualitatively changed: asymptotic hadrons above
such a threshold are not formed from medium modified hadrons anymore, but
rather by new degrees of freedom characterizing the medium. Furthermore, the
disappearance of the squeezed BBC could also serve as a signature of a sudden,
non-equilibrium hadronization scenario from a supercooled quark-gluon plasma
phase.Comment: 12 pages, 3 figures. Presented at 2nd Workshop on Particle
Correlation and Femtoscopy (WPCF 2006), Sao Paulo, Brazil, 9-11 Sep 2006.
Brazilian Journal of Physics (2007) in pres
Searching for squeezed particle-antiparticle correlations in high energy heavy ion collisions
Squeezed correlations of particle-antiparticle pairs were predicted to exist
if the hadron masses were modified in the hot and dense medium formed in high
energy heavy ion collisions. Although well-established theoretically, they have
not yet been observed experimentally. We suggest here a clear method to search
for such signal, by analyzing the squeezed correlation functions in terms of
measurable quantities. We illustrate this suggestion for simulated phi-phi
pairs at RHIC energies.Comment: Revised extended text, one plot added, one figure was moved to
another page in the paper (total of 3 figures, Fig. (2) having parts a, b and
c); added acknowledgmen
Testing the Resolving Power of 2-D K^+ K^+ Interferometry
Adopting a procedure previously proposed to quantitatively study
two-dimensional pion interferometry, an equivalent 2-D chi^2 analysis was
performed to test the resolving power of that method when applied to less
favorable conditions, i.e., if no significant contribution from long lived
resonances is expected, as in kaon interferometry. For that purpose, use is
made of the preliminary E859 K^+ K^+ interferometry data from Si+Au collisions
at 14.6 AGeV/c. As expected, less sensitivity is achieved in the present case,
although it still is possible to distinguish two distinct decoupling
geometries. The present analysis seems to favor scenarios with no resonance
formation at the AGS energy range, if the preliminary K^+ K^+ data are
confirmed. The possible compatibility of data with zero decoupling proper time
interval, conjectured by the 3-D experimental analysis, is also investigated
and is ruled out when considering more realistic dynamical models with
expanding sources. These results, however, clearly evidence the important
influence of the time emission interval on the source effective transverse
dimensions. Furthermore, they strongly emphasize that the static Gaussian
parameterization, commonly used to fit data, cannot be trusted under more
realistic conditions, leading to distorted or even wrong interpretation of the
source parameters!Comment: 11 pages, RevTeX, 4 Postscript figures include
HBT Interferometry for Sonoluminescence Bubble
The two-photon correlation of the light pulse emitted from a sonoluminescence
bubble is discussed. It is shown that several important information about the
mechanism of light emission, such as the time-scale and the shape of the
emission region could be obtained from the HBT interferometry. We also argue
that such a measurement may serve to reject one of the two currently suggested
emission mechanisms, i.e., thermal process versus dynamical Casimir effect.Comment: 13 pages, RevTeX, 2 eps figures include
Integrated Thermal-structural-electromagnetic Design Optimization of Large Space Antenna Reflectors
The requirements for low mass and high electromagnetic (EM) performance in large, flexible space antenna structures is motivating the development of a systematic procedure for antenna design. In contrast to previous work which concentrated on reducing rms distortions of the reflector surface, thereby indirectly increasing antenna performance, the current work involves a direct approach to increasing electromagnetic performance using mathematical optimization. The thermal, structural, and EM analyses are fully integrated in the context of an optimization procedure, and consequently, the interaction of the various responses is accounted for directly and automatically. Preliminary results are presented for sizing cross-sectional areas of a tetrahedral truss reflector. The results indicate potential for this integrated procedure from the standpoint of mass reduction, performance increase, and efficiency of the design process
A computer simulator for development of engineering system design methodologies
A computer program designed to simulate and improve engineering system design methodology is described. The simulator mimics the qualitative behavior and data couplings occurring among the subsystems of a complex engineering system. It eliminates the engineering analyses in the subsystems by replacing them with judiciously chosen analytical functions. With the cost of analysis eliminated, the simulator is used for experimentation with a large variety of candidate algorithms for multilevel design optimization to choose the best ones for the actual application. Thus, the simulator serves as a development tool for multilevel design optimization strategy. The simulator concept, implementation, and status are described and illustrated with examples
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