225,695 research outputs found
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 collisions at = 200 and 500 GeV energies. We report
the total bottom quark production cross section from p+p collisions at
GeV extracted from NPE spectrum and B to D ratios. We also
present the NPE-hadron azimuthal correlations from 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 and collisions
With an effective Lagrangian approach, we give a full analysis on the and reactions by exploring the roles of
various resonances with mass up to 1.72 GeV. We find large contributions from
, , and 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 and
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 , with a bi--invariant orthogonal
decomposition is called positively
curved for commuting pairs, if the sectional curvature vanishes for any tangent
plane in spanned by a linearly independent commuting pair in
. In this paper,we will prove that on the coset space
, in which corresponds to a short
root, admits positively curved metrics for commuting pairs. B. Wilking recently
proved that this 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 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 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 , where 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
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