4,672 research outputs found
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
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
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
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
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
A Computing Method for Sound Propagation Through a Nonuniform Jet Stream
Understanding the principles of jet noise propagation is an essential ingredient of systematic noise reduction research. High speed computer methods offer a unique potential for dealing with complex real life physical systems whereas analytical solutions are restricted to sophisticated idealized models. The classical formulation of sound propagation through a jet flow was found to be inadequate for computer solutions and a more suitable approach was needed. Previous investigations selected the phase and amplitude of the acoustic pressure as dependent variables requiring the solution of a system of nonlinear algebraic equations. The nonlinearities complicated both the analysis and the computation. A reformulation of the convective wave equation in terms of a new set of dependent variables is developed with a special emphasis on its suitability for numerical solutions on fast computers. The technique is very attractive because the resulting equations are linear in nonwaving variables. The computer solution to such a linear system of algebraic equations may be obtained by well-defined and direct means which are conservative of computer time and storage space. Typical examples are illustrated and computational results are compared with available numerical and experimental data
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