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

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

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 $R_{out}/R_{sid}$ 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

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

Search for Squeezed-Pair Correlations at RHIC

Squeezed correlations of particle-antiparticle pairs, also called Back-to-Back Correlations, are predicted to appear if the hadron masses are modified in the hot and dense hadronic medium formed in high energy nucleus-nucleus collisions. Although well-established theoretically, the squeezed-particle correlations have not yet been searched for experimentally in high energy hadronic or heavy ion collisions, clearly requiring optimized forms to experimentally search for this effect. Within a non-relativistic treatment developed earlier we show that one promising way to search for the BBC signal is to look into the squeezed correlation function of pairs of phi-mesons at RHIC energies, plotted in terms of the average momentum of the pair, K12=(k1+k2)/2. This variable's modulus, 2|K12|, is the non-relativistic limit of the variable Q_bbc, introduced herewith. The squeezing effects on the HBT correlation function are also discussed.Comment: 4 pages, 2 figures. To be published in the Proceedings of Quark Matter 2008, Jaipur, Indi