Harmonic moments of the gluon density distribution in AA collisions

By using Monte-Carlo implementations of $k_T$-factorization formula with running-coupling BK unintegrated gluon distributions for nucleus-nucleus collisions, we compute higher order harmonic moments of the initial density distribution for both RHIC(Au+Au@200GeV) and LHC([email protected]) collisions. We study their sensitivity to the size of the valence parton distribution in the nucleon.Comment: 4 pages, 2 figures, references added, figure 2 is replaced by the results of central collision

Numerical Simulation of Non-Abelian Particle-Field Dynamics

Numerical 1D-3V solutions of the Wong-Yang-Mills equations with anisotropic particle momentum distributions are presented. They confirm the existence of plasma instabilities for weak initial fields and their saturation at a level where the particle motion is affected, similar to Abelian plasmas. The isotropization of the particle momenta by strong random fields is shown explicitly, as well as their nearly exponential distribution up to a typical hard scale, which arises from scattering off field fluctuations. By variation of the lattice spacing we show that the effects described here are independent of the UV field modes near the end of the Brioullin zone.Comment: 8 pages, 5 figures; to appear in the proceedings of the "Workshop on Quark-Gluon-Plasma Thermalization", August 10 -- 12, 2005, TU Wien, Austria; http://hep.itp.tuwien.ac.at/qgpth0

Magnetic flux loop in high-energy heavy-ion collisions

We consider the expectation value of a magnetic flux loop in the immediate forward light cone of collisions of heavy nuclei at high energies. Such collisions are characterized by a non-linear scale Q_s where color fields become strong. We find that loops of area greater than ~2/Q_s^2 exhibit area law behavior, which determines the scale of elementary flux excitations ("vortices"). We also estimate the magnetic string tension, sigma_M = 0.12 Q_s^2. By the time t ~ 1/Q_s even small loops satisfy an area law. We describe corrections to the propagator of semi-hard gluons at very early times in the background of fluctuating magnetic fields.Comment: 4 pages, 5 figures; v2: added plot of Z(N) part of loop in fig.1; v3: added magnetic loop for asymmetric projectile/target saturation momenta, estimate of vortex density, and an appendix; v4: corrected outline of perturbative calculation of Wilson loop; to appear in PR

Can We Extract Lambda-Lambda Interaction from Two-Particle Momentum Correlation ?

We analyze the invariant mass spectrum of Lambda-Lambda in $^{12}C(K^-,K^+ Lambda Lambda)$ reaction at P(K^+)=1.65 GeV/c by using a combined framework of IntraNuclear Cascade (INC) model and the correlation function technique. The observed enhancement at low-invariant masses can be well reproduced with attractive Lambda-Lambda interactions with the scattering length either in the range a = -6 \sim -4 fm (no bound state) or a = 7 \sim 12 fm (with bound state). We also discuss Lambda-Lambda correlation functions in central relativistic heavy-ion collisions as a possible way to eliminate this discrete ambiguity.Comment: 4 Pages, LaTeX with psfig, embedded 4 ps figures. Talk given at KEK-Tanashi Int. Symp. on "Physics of Hadrons and Nuclei", 14-17 Dec. 1998, Tokyo, Japan, Nuclear Physics A, to appea

Probing neutron-proton dynamics by pions

In order to investigate the nuclear symmetry energy at high density, we study the pion production in central collisions of neutron-rich nuclei ${}^{132}\mathrm{Sn}+{}^{124}\mathrm{Sn}$ at 300 MeV/nucleon using a new approach by combining the antisymmetrized molecular dynamics (AMD) and a hadronic cascade model (JAM). The dynamics of neutrons and protons is solved by AMD, and then pions and $\Delta$ resonances in the reaction process are handled by JAM. We see the mechanism how the $\Delta$ resonance and pions are produced reflecting the dynamics of neutrons and protons. We also investigate the impacts of cluster correlations as well as of the high-density symmetry energy on the nucleon dynamics and consequently on the pion ratio. We find that the $\Delta^-/\Delta^{++}$ production ratio agrees very well with the neutron-proton squared ratio $(N/Z)^2$ in the high-density and high-momentum region. We show quantitatively that $\Delta$ production ratio, and therefore $(N/Z)^2$, are directly reflected in the $\pi^-/\pi^+$ ratio, with modification in the final stage of the reaction.Comment: 14 pages, 10 figures; Figures 3-8 are updated with corrected numerical results. No change in the main conclusion