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R_{out}/R_{sid} and Opacity at RHIC  [PDF]
Larry McLerran,Sandra S. Padula
Physics , 2002,
Abstract: One of the most dramatic results from the first RHIC run are the STAR results for pi+- pi+- interferometry. They showed that the ratio of the so-called R_{out} and R_{sid} radii seem to decrease below unity for increasing transverse momentum of the pair (K_T). This was subsequently confirmed by PHENIX, which also extended the K_T range of the measurements. We consider here the effects of opacity of the nuclei on this ratio, and find that such a small value is consistent with surface emission from an opaque source.
Pion freeze-out through HBT correlation in HICs from AGS/FAIR to RHIC energies  [PDF]
Qingfeng Li
Physics , 2007,
Abstract: In this talk we present the results of two-pion HBT correlation at freeze-out in heavy ion collisions (HICs) from AGS to RHIC energies. The UrQMD hadron-string transport model as well as the CRAB analyzing program are adopted. Based on the cascade mode, in general, the calculations are satisfying and well in line with the experimental data although discrepancies are not negligible. Such as: I), the HBT time-related puzzle exists at all energies. II), at low AGS energies, the calculated volume as well as the mean free path of pion source at freeze-out are lower than data. It implies that a better description of interactions of particles at early stage of HICs is required.
Pion freeze-out as seen through HBT correlations in heavy ion collisions from FAIR/AGS to RHIC energies  [PDF]
Qingfeng Li,Marcus Bleicher,Horst Stoecker
Physics , 2007, DOI: 10.1088/0954-3899/34/9/012
Abstract: We perform a systematic analysis of several HBT parameters in heavy ion collisions from $E_{\rm beam}=2$ AGeV to $\sqrt {s_{\rm NN}}=200$ GeV within the UrQMD transport approach and compare the results to experimental data where available. We find that the 'lifetime' of the emission source as calculated from $\tau \sim \sqrt{R_O^{2}-R_S^{2}}$, is larger than the experimentally observed values at all investigated energies. The calculated volume of the pion source ($V_f$) is found to increase monotonously with increasing beam energy and the experimentally observed decrease of the measured $V_f$ at AGS is not seen. Finally, we calculate the mean free path $\lambda_f=0.5-1$ fm of pions at freeze-out and find a good description of the experimental data above the AGS energy region, supporting the suggestion of a universal kinetic decoupling criterion up to the highest RHIC energies.
Sid knocks them out
John C Rockett
Genome Biology , 2002, DOI: 10.1186/gb-2002-3-7-reports0034
Abstract: In a genetic screen, three major complementation groups with systemic RNAi-defective (SID) phenotypes were identified. One of these was further characterized by a variety of methods. The cDNA sequence of the responsible gene (sid-1) was isolated, where and when the gene is expressed was determined, and the overall protein structure predicted from its sequence. The sid-1 gene is initially expressed in late-stage embryos and continually thereafter in nearly all non-neural cell types, with the highest levels expressed in cells and tissues exposed to the environment. At the subcellular level, significant enrichment of sid-1 was seen at the cell periphery, a location consistent with the presence of predicted transmembrane regions in the protein.The authors constructed a transgenic strain (HC57) of C. elegans that allows simultaneous monitoring of localized RNAi (myo-2::GFP, in the pharyngeal muscles) and systemic RNAi (myo-3::GFP, in the body wall muscles) through the expression of green fluorescent protein (GFP). RNAi was initiated through a third transgene (myo-2::GFP dsRNA) under control of the pharynx-specific myo-2 promoter. Mutants resistant to systemic RNAi were identified by screening for those that were resistant to systemic RNAi of myo-3, but sensitive to the local RNAi of myo-2.Supplementary data to Science295:2456-2459 include figures and details of experimental procedures and are available at free of charge. The homepage of Craig Hunter's laboratory contains a link to a full copy of the paper.The authors suggest that, on the basis of the proposed protein structure, SID-1 may act as a channel through which dsRNA can pass between cells. In addition, SID-1 has strong similarity to predicted human and mouse proteins, suggesting the possibility that RNAi may be systemic in mammals, and that the mechanism may share some components found in C. elegans.In this classic piece of genetic work, Winston et al. demonstrated considerable skill and persistence in teasing ou
The early thermalization and HBT puzzles at RHIC  [PDF]
Wojciech Florkowski
Physics , 2010,
Abstract: The early thermalization and HBT puzzles in relativistic heavy-ion collisions studied at RHIC are shortly reviewed. The results of recent hydrodynamic calculations that shed light on these two intriguing issues are presented. In particular, the role of the elliptic flow as a signature of early thermalization is critically examined.
Solution of the RHIC HBT puzzle with Gaussian initial conditions  [PDF]
W. Florkowski,W. Broniowski,M. Chojnacki,A. Kisiel
Physics , 2008, DOI: 10.1088/0954-3899/36/6/064067
Abstract: It is argued that the consistent description of the transverse-momentum spectra, elliptic flow, and the HBT radii in the relativistic heavy-ion collisions studied at RHIC may be obtained within the hydrodynamic model if one uses the Gaussian profile for the initial energy density in the transverse plane. Moreover, we show that the results obtained in the scenario with an early start of hydrodynamics (at the proper time tau0 = 0.25 fm) are practically equivalent to the results obtained in the model where the hydrodynamics is preceded by the free-streaming stage of partons (in the proper time interval 0.25 fm < tau < 1 fm) which suddenly equilibrate and with the help of the Landau matching conditions are transformed into the hydrodynamic regime (at the proper time tau0 = 1 fm).
Quantum Opacity, the RHIC HBT Puzzle, and the Chiral Phase Transition  [PDF]
John G. Cramer,Gerald A. Miller,Jackson M. S. Wu,Jin-Hee Yoon
Physics , 2004, DOI: 10.1103/PhysRevLett.94.102302
Abstract: 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 on "Quantum Opacity, the RHIC HBT Puzzle, and the Chiral Phase Transition"  [PDF]
PHOBOS Collaboration,B. B. Back
Physics , 2005,
Abstract: We are submitting a comment on the paper "Quantum Opacity, the RHIC HBT Puzzle, and the Chiral Phase Transition" by J.G. Cramer, G.A. Miller, J.M.S. Wu and J. Yoon, published in Phys. Rev. Lett. 94, 102302 (2005).
Comparison of hadronic rescattering calculations of elliptic flow and HBT with measurements from RHIC  [PDF]
T. J. Humanic
Physics , 2002, DOI: 10.1016/S0375-9474(02)01551-8
Abstract: Results from the data obtained in the first physics run of the Relativistic Heavy Ion Collider (RHIC) have shown suprisingly large elliptic flow and suprisingly small HBT radii. Attempts to explain both results in a consistant picture have so far been unsuccessful. The present work shows that a simple thermal-like initial state model coupled to a hadronic rescattering calculation can explain reasonably well both elliptic flow and HBT results from RHIC. The calculation suggests a very early hadronization time of about 1 fm/c after the initial collision of the nuclei.
Early anisotropic hydrodynamics and the RHIC early-thermalization and HBT puzzles  [PDF]
Radoslaw Ryblewski,Wojciech Florkowski
Physics , 2010, DOI: 10.1103/PhysRevC.82.024903
Abstract: We address the problem if the early thermalization and HBT puzzles in relativistic heavy-ion collisions may be solved by the assumption that the early dynamics of the produced matter is locally anisotropic. The hybrid model describing the purely transverse hydrodynamic evolution followed by the perfect-fluid hydrodynamic stage is constructed. The transition from the transverse to perfect-fluid hydrodynamics is described by the Landau matching conditions applied at a fixed proper time. The global fit to the RHIC data reproduces the soft hadronic observables (the pion, kaon, and the proton spectra, the pion and kaon elliptic flow, and the pion HBT radii) with the accuracy of about 20%. These results indicate that the assumption of the very fast thermalization may be relaxed. In addition, the presented model suggests that a large part of the inconsistencies between the theoretical and experimental HBT results may be removed.
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