Elliptical Flow in Relativistic Ion Collisions at s^(1/2)= 200 A GeV

A consistent picture of the Au+Au and D+Au, s^1/2 = 200 A GeV measurements at RHIC obtained with the PHENIX, STAR, PHOBOS and BRAHMS detectors including both the rapidity and transverse momentum spectra was previously developed with the simulation LUCIFER. The approach was modeled on the early production of a fluid of pre-hadrons after the completion of an initial, phase of high energy interactions. The formation of pre-hadrons is discussed here, in a perturbative QCD approach as advocated by Kopeliovich, Nemchik and Schmidt. In the second phase of LUCIFER, a considerably lower energy hadron-like cascade ensues. Since the dominant collisions occurring in this latter phase are meson-meson in character while the initial collisions are between baryons, i.e. both involve hadron sized interaction cross-sections, there is good reason to suspect that the observed elliptical flow will be produced naturally, and this is indeed found to be the case.Comment: 7 pages, 6 figure

The H-Dibaryon and the Hard Core

The H dibaryon, a single, triply magic bag containing two up, two down and two strange quarks, has long been sought after in a variety of experiments. Its creation has been attempted in $K^-$, proton and most recently in relativistic heavy ion induced reactions. We concentrate on the latter, but our conclusions are more generally applicable. The two baryons coalescing to form the single dibaryon, likely $\Lambda \Lambda$ in the case of heavy ions, must penetrate the short range repulsive barrier which is expected to exist between them. We find that this barrier can profoundly affect the probability of producing the H state, should it actually exist.Comment: 9 pages including 4 figure

Recall termination in free recall

Although much is known about the dynamics of\ud memory search in the free recall task, relatively little is\ud known about the factors related to recall termination. Rean-\ud alyzing individual trial data from 14 prior studies (1,079\ud participants in 28,015 trials) and defining termination as\ud occurring when a final response is followed by a long\ud nonresponse interval, we observed that termination proba-\ud bility increased throughout the recall period and that retriev-\ud al was more likely to terminate following an error than\ud following a correct response. Among errors, termination\ud probability was higher following prior-list intrusions and\ud repetitions than following extralist intrusions. To verify that\ud this pattern of results can be seen in a single study, we report\ud a new experiment in which 80 participants contributed recall\ud data from a total of 9,122 trials. This experiment replicated\ud the pattern observed in the aggregate analysis of the prior\ud studies.\u

Cayley-Tree Ising Model with Antiferromagnetic Nearest-Neighbor and Ferromagnetic Equivalent-Neighbor Interactions

The phase diagram of the Ising model with antiferromagnetic nearest-neighbor interactions and ferromagnetic equivalent-neighbor interactions on the Cayley tree is determined exactly. A nonuniversal critical line separates the disordered and the ordered phases. A line of first-order transitions separating ferromagnetic order from antiferromagnetic order ends in the midst of the ordered phase at a classical ordered critical point. For a small range of values of the ratio of the two couplings, two transitions occur as the temperature is varied. In this case the uniform magnetization is not a monotonic function of the temperature

Light-induced weak ferromagnetism through nonlinear magnonic rectification

Rectification describes the generation of a quasistatic component from an oscillating field, such as an electric polarization in optical rectification, or a structural distortion in nonlinear phononic rectification. Here, we present a third fundamental process for magnetization, in which spin precession is rectified along the coordinates of a nonlinearly driven magnon mode in an antiferromagnet. We demonstrate theoretically that a quasistatic magnetization can be induced by transient spin canting in response to the coherent excitation of a chiral phonon mode that produces an effective magnetic field for the spins. This mechanism, which we call nonlinear magnonic rectification, is generally applicable to magnetic systems that exhibit degenerate chiral phonon modes. Our result serves as an example of light-induced weak ferromagnetism and provides a promising avenue to creating nonequilibrium spin configurations

Inclusive Particle Spectra at RHIC

A simulation is performed of the recently reported data from PHOBOS at energies of 56 and 130 A GeV using the relativistic heavy ion cascade LUCIFER which had previously given a good description of the NA49 inclusive spectra at E=17.2 A GeV. The results compare well with these early measurements at RHIC.Comment: 4 pages, 2 figure

Suppression of High Transverse Momentum π0\pi^0 Spectra in Au+Au Collisions at RHIC

Au+Au, $s^{1/2} = 200$ A GeV measurements at RHIC, obtained with the PHENIX, STAR, PHOBOS and BRAHMS detectors, have all indicated a suppression of neutral pion production, relative to an appropriately normalized NN level. For central collisions and vanishing pseudo-rapidity these experiments exhibit suppression in charged meson production, especially at medium to large transverse momenta. In the PHENIX experiment similar behavior has been reported for $\pi^0$ spectra. In a recent work on the simpler D+Au interaction, to be considered perhaps as a tune-up for Au+Au, we reported on a pre-hadronic cascade mechanism which explains the mixed observation of moderately reduced $p_\perp$ suppression at higher pseudo-rapidity as well as the Cronin enhancement at mid-rapidity. Here we present the extension of this work to the more massive ion-ion collisions. Our major thesis is that much of the suppression is generated in a late stage cascade of colourless pre-hadrons produced after an initial short-lived coloured phase. We present a pQCD argument to justify this approach and to estimate the time duration $\tau_p$ of this initial phase. Of essential importance is the brevity in time of the coloured phase existence relative to that of the strongly interacting pre-hadron phase. The split into two phases is of course not sharp in time, but adequate for treating the suppression of moderate and high $p_\perp$ mesons.Comment: 19 pages, 10 figure

On the D-term of the nucleon generalized parton distributions

It is known that some of the deeply-virtual-Compton-scattering observables, for instance, the beam-charge asymmetry in the hard electroproduction of real photons on the nucleon, are extremely sensitive to the magnitude of D-term appearing in the parameterization of the generalized parton distributions. We report a theoretical analysis of both the isoscalar and isovector parts of the nucleon D-term within the framework of the chiral quark soliton model, without recourse to the derivative expansion type approximation used in previous works.Comment: 10 pages, 2 eps-figures, small improvements, version to appear in Phys. Lett.

J/Psi Production by Charm Quark Coalescence

Production of $c\bar c$ pairs in elementary hadron-hadron collisions is introduced in a simulation of relativistic heavy ion collisions. Coalescence of charmed quarks and antiquarks into various charmonium states is performed and the results are compared to PHENIX J$/\psi$ Au+Au data. The $\chi$ and $\psi$' bound states must be included as well as the ground state J$/\psi$, given the appreciable feeding from the excited states down to the J$/\psi$ via gamma decays. Charmonium coalescence is found to take place at relatively late times: generally after $c$($\bar c$)-medium interactions have ceased. Direct production of charmonia through hadron-hadron interactions, {\it ie.} without explicit presence of charm quarks, occurring only at early times, is suppressed by collisions with comoving particles and accounts for some $\sim 5\%$ of the total J$/\psi$ production. Coalescence is especially sensitive to the level of open charm production, scaling naively as $n_{c\bar c}^2$. The J$/\psi$ transverse momentum distribution is dependent on the charm quark transverse momentum distribution and early charm quark-medium interaction, thus providing a glimpse of the initial collision history.Comment: 19 pages, 10 figure

The Nystrom plus Correction Method for Solving Bound State Equations in Momentum Space

A new method is presented for solving the momentum-space Schrodinger equation with a linear potential. The Lande-subtracted momentum space integral equation can be transformed into a matrix equation by the Nystrom method. The method produces only approximate eigenvalues in the cases of singular potentials such as the linear potential. The eigenvalues generated by the Nystrom method can be improved by calculating the numerical errors and adding the appropriate corrections. The end results are more accurate eigenvalues than those generated by the basis function method. The method is also shown to work for a relativistic equation such as the Thompson equation.Comment: Revtex, 21 pages, 4 tables, to be published in Physical Review