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Register a new userTwo- and Three-Pion Interferometry for a Nonchaotic Source in Relativistic Nuclear Collisions
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Authors
Hiroki Nakamura
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Two- and three-pion correlation functions are investigated for a source that is not fully chaotic. Various models are examined to describe the source. The chaoticity and weight factor are evaluated in each model as measures of the strength of correlations and compared to experimental results. A new measure of three-pion correlation is also suggested.
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Three-pion interferometry is investigated for new information on the space-time structure of the pion source created in ultra-relativistic heavy-ion collisions. The two- and three-pion correlations are numerically computed for incoherent source functions based on the Bjorken hydrodynamical model, over a wide range of the kinematic variables. New information provided by three-pion interferometry, different from that provided by two-pion interferometry, should appear in the phases of the Fourier transform of the source function. Variables are identified that would be sensitive to the phases and suitable for observation. For a positive, chaotic source function, however, a variation of the three-pion phase is found to be difficult to extract from experiments. Effects of asymmetry of the source function are also examined.
We investigate a domain-structured source in the pion interferometry of relativistic nuclear collisions. The source emits coherent pions intermittently with the background of chaotic pions. The coherent pions examined are either of a general nature or of disoriented chiral condensate. Two- and three-pion correlations for the source are shown to agree well with the recent NA44 experimental data.
Two- and three-pion correlations are investigated in cases when disoriented chiral condensate (DCC) occurs. A chaoticity and weight factor are used as measures of two- and three-pion correlations, and the various models for DCC are investigated. Some models are found to yield the chaoticity and weight factor in a reasonable agreement with recent experimental data.
The production of mesons in ultra-peripheral collisions of relativistic heavy ions is re-analyzed using a projection technique to calculate the amplitudes for the appropriate Feynman diagrams. The virtuality of the exchanged photons is fully accounted for in this approach. In the case of two-photon fusion, it is explicitly shown that the inclusion of nuclear form factors validates the equivalent photon approximation. However, this does not apply to three-photon fusion cross sections. The cross section of J/psi production in ultra-peripheral collisions at RHIC and LHC are shown to be much smaller than the cross sections for the production of C=even mesons of similar masses.
Multiplicity distributions of hadrons produced in central nucleus-nucleus collisions are studied within the hadron-resonance gas model in the large volume limit. In the canonical ensemble conservation of three charges (baryon number, electric charge, and strangeness) is enforced. In addition, in the micro-canonical ensemble energy conservation is included. An analytical method is used to account for resonance decays. Multiplicity distributions and scaled variances for negatively charged hadrons are presented along the chemical freeze-out line of central Pb+Pb (Au+Au) collisions from SIS to LHC energies. Predictions obtained within different statistical ensembles are compared with preliminary NA49 experimental results on central Pb+Pb collisions in the SPS energy range. The measured fluctuations are significantly narrower than a Poisson reference distribution, and clearly favor expectations for the micro-canonical ensemble.
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