Global variables and identified hadrons in the PHENIX experiment

PHENIX measurements related to global variables and identified hadrons are discussed. These include two-pion correlations, elliptic flow, and dN/dη. Measurements of event-by-event fluctuations in mean transverse momentum, mean transverse energy, and net charge are presented for particles within the PHENIX acceptance. The centrality dependence of these measurements is also discussed.     

Femtoscopic results in Au + Au and p + p from PHENIX at RHIC

Ultra-relativistic gold-gold and proton-proton collisions are investigated in the experiments of the Relativistic Heavy Ion Collider (RHIC). In the last several years large amount of results were revealed about the matter created in these collisions. The latest PHENIX results for femtoscopy and correlations are reviewed in this paper. Bose-Einstein correlations of charged kaons in 200 GeV Au + Au collisions and of charged pions in 200 GeV p + p collisions are shown. They are both compatible with previous measurements of charged pions in gold-gold collisions, with respect to transverse mass or number of participants scaling.     

Femtoscopy in p+p vs. heavy ion collisions in STAR

The geometric substructure of the particle-emitting source has been characterized via two-particle interferometry by the STAR collaboration for several energies and colliding systems at RHIC. In heavy ion collisions the m_T dependence of femtoscopic radii has been observed for all particle types by several experiments at different collision energies. This dependence has been thought to arise from space-momentum correlations generated by collective flow. On the other hand, there are several reports of a similar m_T dependence by experiments measuring elementary particle collisions. Here, quite different physical mechanisms – including resonances, strings, and uncertainty arguments – have been proposed to explain the dependence. Determining the differences or similarities in the space-time physics driving the signal in heavy ion versus p+p collisions requires a direct comparison of m_T dependence of the radii. Such a comparison has, until now, been sorely lacking. STAR data allow, for the first time, such a direct comparison between A+A, d+A, and p+p collisions, at the same energy, measured in the same detector, and using the same analysis techniques. Surprisingly, our preliminary results indicate an m_T-independent scaling of the femtoscopic radii with overall system size. Possible physics implications of these observations will be discussed, and the importance of long-range non-femtoscopic correlations for low multiplicity collisions will be emphasized. PACS 25.75.Gz; 25.75.-q     

Output from an atom laser: theory vs. experiment

Atom lasers based on rf-outcoupling can be described by a set of coupled generalized Gross–Pitaevskii equations (GPE). We compare the theoretical predictions obtained by numerically integrating the time-dependent GPE of an effective one-dimensional model with recently measured experimental data for the F=2 and F=1 states of Rb-87. We conclude that the output of a rf atom-laser can be described by this model in a satisfactory way. Received: 15 June 1999 / Revised version: 9 September 1999 / Published online: 10 November 1999     

Oscillating neutrinos: theory vs experiment

Possible hints on neutrino masses are reviewed. They come from the deficits in the solar as well as atmospheric neutrinos and from need of a significant amount of hot component in the dark matter of the universe. The role of three generation mixing in simultaneously solving the solar and atmospheric neutrino problem is discussed. All the three hints can be reconciled if three neutrinos are almost degenerate. Models for neutrino masses and mixing implied by the above hints are briefly discussed.     

Dendrogramic Representation of Data: CHSH Violation vs. Nonergodicity

This paper is devoted to the foundational problems of dendrogramic holographic theory (DH theory). We used the ontic–epistemic (implicate–explicate order) methodology. The epistemic counterpart is based on the representation of data by dendrograms constructed with hierarchic clustering algorithms. The ontic universe is described as a p-adic tree; it is zero-dimensional, totally disconnected, disordered, and bounded (in p-adic ultrametric spaces). Classical–quantum interrelations lose their sharpness; generally, simple dendrograms are “more quantum” than complex ones. We used the CHSH inequality as a measure of quantum-likeness. We demonstrate that it can be violated by classical experimental data represented by dendrograms. The seed of this violation is neither nonlocality nor a rejection of realism, but the nonergodicity of dendrogramic time series. Generally, the violation of ergodicity is one of the basic features of DH theory. The dendrogramic representation leads to the local realistic model that violates the CHSH inequality. We also considered DH theory for Minkowski geometry and monitored the dependence of CHSH violation and nonergodicity on geometry, as well as a Lorentz transformation of data.     

Far-infrared absorption in small metal particles: Non-local theory

The non-local theory of electromagnetic response has been applied to study the far-infrared absorption in small particles. The absorption coefficient appears to be described by the same expression as that given by the local theory, except that the effective electronic scattering time in the magnetic-dipole absorption differs strongly from that in the electric-dipole absorption. In the latter case the effective electronic free-path is highly sensitive to the scattering conditions on the particle boundary and changes from about the particle diameter for diffuse scattering to the electronic mean free-path in a bulk metal sample for specular scattering. This can explain observed large far-infrared absorption. Quantum effects are also discussed briefly.     

Simplicial vs. continuum string theory and loop equations

We derive loop equations in a scalar matrix field theory. We discuss their solutions in terms of simplicial string theory—the theory describing embeddings of two-dimensional simplicial complexes into the spacetime of the matrix field theory. This relation between the loop equations and the simplicial string theory gives further arguments that favor one of the statements of the paper hep-th/0407018. The statement is that there is an equivalence between the partition function of the simplicial string theory and the functional integral in a continuum string theory—the theory describing embeddings of smooth two-dimensional world-sheets into the spacetime of the matrix field theory in question.     

Interactions of like-charged rods at low temperatures: Analytical theory vs. simulations

We investigate a system consisting of two like-charged infinitely long rods and neutralizing counterions at low temperatures, using both analytic theory and simulations. With some reasonable approximations we can analytically solve for several ground-state structures of the model, starting with states where all counterions are lined up in the gap between the rods, over planar configurations, where the counterions are divided up into a fraction which resides between the rods, and counterions which are located on the outer surfaces, up to configurations which cover the full rod surfaces. Using parallel tempering simulations, we are able to study the system over a wide range of temperatures. At low temperatures we find good agreement with our T = 0 results. At higher temperatures, the strong coupling (SC) theory delivers qualitatively better results. We furthermore demonstrate that for the SC theory and our ground-state approximations to yield quantitative agreement, three parameters are required to be large, the strong-coupling parameter Ξ, the Rouzina-Bloomfield parameter, and the ratio of the average distance of the counterions to the radius of the rods. In the case of the latter ratio being small, our T = 0 results show better agreement with the simulation data at very low temperatures.     

J/Ψ measurement in p+p, d+Au and Au+Au collisions by the PHENIX experiment at RHIC

J/Ψ’s are produced mostly via interactions involving gluons, and are a sensitive probe of the gluon structure function and its modification in nuclei. They are also considered as a leading signal for studying the creation of hot and dense matter in relativistic heavy ion collision. Measurement of J/Ψ production in different colliding systems is important for understanding the nuclear modification factor, and setting a baseline for the study of J/Ψ suppression in heavy ion collisions. In this talk we report the latest results on J/Ψ measurements by the PHENIX experiment at RHIC in p+p; d+Au, and Au+Au collisions at backward, forward, and mid-rapidity. Nuclear effects are studied as a function of transverse momentum, rapidity and centrality.     

Isothermal vs. isentropic description of protoneutron stars in the Brueckner-Bethe-Goldstone theory

We study the structure of hadronic protoneutron stars within the finite-temperature Brueckner-Bethe-Goldstone theoretical approach. Assuming beta-equilibrated nuclear matter with nucleons and leptons in the stellar core, with isothermal or isentropic profile,we show that particle populations and equation of state are very similar. As far as the maximum mass is concerned, we find that its value turns out to be almost independent of T, while a slight decrease is observed in the isentropic case, due to the enhanced proton fraction in the high-density range. The text was submitted by the authors in English.     

Unstable particles in a self-consistent field theory

We indicate how unstable particles can be introduced into the self-consistent field theory formulation of Umezawa where the equal-time commutation relations for Heisenberg fields are derived and not assumed. The Lee model is used to illustrate the results.     

On the theory of high-velocity particles: A comment

An argument claiming to prove two familiar consequences of special relativity, starting from the wave-particle duality of L. de Broglie, is found to be circular.     

High p(T) azimuthal asymmetry in noncentral A + A at RHIC

The high p(T)>3 GeV azimuthal asymmetry, v(2)(p(T)), in noncentral nuclear collisions at RHIC is shown to be a sensitive measure of the initial parton density distribution of the produced quark-gluon plasma. A generalization of the Gyulassy-Lévai-Vitev non-Abelian energy loss formalism including Bjorken (1+1)D expansion as well as important kinematic constraints is used.     

Remarks on identical particles in de Broglie-Bohm theory

It is argued that the topological approach to the (anti-)symmetrisation condition for the quantum state of a collection of identical particles, defined in the “reduced” configuration space, is particularly natural from the perspective of de Broglie-Bohm pilot-wave theory.