STAR Measurements of Bottom to Charm Ratio and Heavy Quark Interaction with the QCD Medium through Non-Photonic Electron-Hadron Correlations

We present STAR measurements of relative charm and bottom contributions to NPE from $p+p$ collisions at $\sqrt{s}$= 200 and 500 GeV energies. We report the total bottom quark production cross section from p+p collisions at $\sqrt{s}= 200$ GeV extracted from NPE spectrum and B to D ratios. We also present the NPE-hadron azimuthal correlations from $Au+Au$ collisions at \sqrtsNN = 200 GeV from the 2010 RHIC run where we have collected high statistics data set with low photonic conversion background.Comment: 4 pages, 3 figures. Proceedings for XXII International Conference on Ultra-relativistic Nucleus-Nucleus Collision (Quark Matter 2011), 22 - 28 May 2011, Annecy, Franc

Double pion production in NNNN and NˉN\bar{N}N collisions

With an effective Lagrangian approach, we give a full analysis on the $NN \to NN\pi\pi$ and $\bar{N}N\to \bar{N}N\pi\pi$ reactions by exploring the roles of various resonances with mass up to 1.72 GeV. We find large contributions from $\Delta$, $N^*(1440)$, $\Delta(1600)$ and $\Delta(1620)$ resonances. Our calculations also indicate sizeable contributions from nucleon poles for the energies close to the threshold. A good description to the existing data of different isospin channels of $NN\to NN\pi\pi$ and $\bar{N}N\to \bar{N}N\pi\pi$ for beam energies up to 2.2 GeV is reached. Our results provide important implications to the ABC effect and guildlines to the future experimental projects at COSY, HADES and HIRFL-CSR. We point out that the \={P}ANDA at FAIR could be an essential place for studying the properties of baryon resonances and the data with baryon and anti-baryon in final states are worth analyzing.Comment: Invited plenary talk at the 11th International Workshop on Meson Production, Properties and Interaction (MESON2010), 10-15 June, 2010, Krakow, Polan

Sp(2)/U(1) and a Positive Curvature Problem

A compact Riemannian homogeneous space $G/H$, with a bi--invariant orthogonal decomposition $\mathfrak{g}=\mathfrak{h}+\mathfrak{m}$ is called positively curved for commuting pairs, if the sectional curvature vanishes for any tangent plane in $T_{eH}(G/H)$ spanned by a linearly independent commuting pair in $\mathfrak{m}$. In this paper,we will prove that on the coset space $\mathrm{Sp}(2)/\mathrm{U}(1)$, in which $\mathrm{U}(1)$ corresponds to a short root, admits positively curved metrics for commuting pairs. B. Wilking recently proved that this $\mathrm{Sp}(2)/\mathrm{U}(1)$ can not be positively curved in the general sense. This is the first example to distinguish the set of compact coset spaces admitting positively curved metrics, and that for metrics positively curved only for commuting pairs.Comment: In this Version 2 we incorporated an argument of Burkhard Wilking, and we modified the abstract, introduction and title to reflect that chang

Thermalization of gluon matter including gg<->ggg interactions

Within a pQCD inspired kinetic parton cascade we simulate the space time evolution of gluons which are produced initially in a heavy ion collision at RHIC energy. The inelastic gluonic interactions $gg \leftrightarrow ggg$ do play an important role: For various initial conditions it is found that thermalization and the close to ideal fluid dynamical behaviour sets in at very early times. Special emphasis is put on color glass condensate initial conditions and the `bottom up thermalization' scenario. Off-equilibrium $3\to 2$ processes make up the very beginning of the evolution leading to an initial decrease in gluon number and a temporary avalanche of the gluon momentum distribution to higher transversal momenta.Comment: 6 pages, 8 figures, Talk given at International Conference on Strong and Electroweak Matter (SEWM 2006), BNL, New York, May 200

Linewidth Differences of Neutrals and Ions Induced by MHD Turbulence

We address the problem of the difference of line widths of neutrals and ions observed from molecular clouds and explore whether this difference can arise from the effects of magnetohydrodynamic (MHD) turbulence acting on partially ionized gas. Among the three fundamental modes of MHD turbulence, we find fast modes do not contribute to linewidth differences, whereas slow modes can have an effect on different line widths for certain parameters. We focus on Alfv\'{e}nic component because they contain most of the turbulent energy, and consider the damping of this component taking into account both neutral-ion collisions and neutral viscosity. We consider different regimes of turbulence corresponding to different media magnetizations and turbulent drivings. In the case of super-Alfv\'{e}nic turbulence, when the damping scale of Alfv\'{e}nic turbulence is below $l_A$, where $l_A$ is the injection scale of anisotropic GS95-type turbulence, the linewidth difference does not depend on the magnetic field strength. While for other turbulent regimes, the dependence is present. For instance, the difference between the squares of the neutral and ion velocity dispersions in strong sub-Alfv\'{e}nic turbulence allows evaluation of magnetic field. We discuss earlier findings on the neutral-ion linewidth differences in the literature and compare the expressions for magnetic field we obtain with those published earlier.Comment: 26 pages, 8 figure