4,482 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
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
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
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
Possible Origin of RHIC R_{out}/R_{sid} HBT Results
The effects of opacity of the nuclei together with a blackbody type of
emission along the system history are considered as a means to explain the
ratio observed by STAR and PHENIX collaborations at RHIC.
Within our model, no flow is required to explain the data trend of this ratio
for large surface emissivities.Comment: 4 pages, 2 Postscript figures, uses espcrc1.sty. Talk presented at
Quark Matter 2002, Nantes, France, July 18-24, 2002; to appear in the
proceedings (Nucl. Phys. A
Squeezed Fermions at Relativistic Heavy Ion Colliders
Large back-to-back correlations of observable fermion -- anti-fermion pairs
are predicted to appear, if the mass of the fermions is modified in a
thermalized medium. The back-to-back correlations of protons and anti-protons
are experimentally observable in ultra-relativistic heavy ion collisions,
similarly to the Andreev reflection of electrons off the boundary of a
superconductor. While quantum statistics suppresses the probability of
observing pairs of fermions with nearby momenta, the fermionic back-to-back
correlations are positive and of similar strength to bosonic back-to-back
correlations.Comment: LaTeX, ReVTeX 12 pages, uses epsf.sty, 2 eps figures, improved
presentatio
Back-to-Back Correlations for Finite Expanding Fireballs
Back-to-Back Correlations of particle-antiparticle pairs are related to the
in-medium mass-modification and squeezing of the quanta involved. They are
predicted to appear when hot and dense hadronic matter is formed in high energy
nucleus-nucleus collisions. The survival and magnitude of the Back-to-Back
Correlations of boson-antiboson pairs generated by in-medium mass modifications
are studied here in the case of a thermalized, finite-sized, spherically
symmetric expanding medium. We show that the BBC signal indeed survives the
finite-time emission, as well as the expansion and flow effects, with
sufficient intensity to be observed at RHIC.Comment: 24 pages, 4 figure
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