86,923 research outputs found
Review of the "Bottom-Up" scenario
Thermalization of a longitudinally expanding color glass condensate with
Bjorken boost invariant geometry is investigated within parton cascade BAMPS.
Our main focus lies on the detailed comparison of thermalization, observed in
BAMPS with that suggested in the Bottom-Up scenario. We demonstrate that the
tremendous production of soft gluons via , which is shown in the
Bottom-Up picture as the dominant process during the early preequilibration,
will not occur in heavy ion collisions at RHIC and LHC energies, because the
back reaction hinders the absolute particle multiplication.
Moreover, contrary to the Bottom-Up scenario, soft and hard gluons thermalize
at the same time. The time scale of thermal equilibration in BAMPS calculations
is of order \as^{-2} (\ln \as)^{-2} Q_s^{-1}. After this time the gluon
system exhibits nearly hydrodynamic behavior. The shear viscosity to entropy
density ratio has a weak dependence on and lies close to the lower bound
of the AdS/CFT conjecture.Comment: Quark Matter 2008 Proceeding
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
Fluence dependent femtosecond quasi-particle and Eu^{2+} -spin relaxation dynamics in EuFe_{2}(As,P)_{2}
We investigated temperature and fluence dependent dynamics of the time
resolved optical reflectivity in undoped spin-density-wave (SDW) and doped
superconducting (SC) EuFe(As,P) with emphasis on the ordered
Eu-spin temperature region. The data indicate that the SDW order
coexists at low temperature with the SC and Eu-ferromagnetic order.
Increasing the excitation fluence leads to a thermal suppression of the
Eu-spin order due to the crystal-lattice heating while the SDW order is
suppressed nonthermally at a higher fluence
News on PHOTOS Monte Carlo: gamma^* -> pi^+ pi^-(gamma) and K^\pm -> pi^+ pi^- e^\pm nu (gamma)
PHOTOS Monte Carlo is widely used for simulating QED effects in decay of
intermediate particles and resonances. It can be easily connected to other main
process generators. In this paper we consider decaying processes gamma^* ->
pi^+ pi^-(gamma) and K^\pm -> pi^+ pi^- e^\pm nu (gamma) in the framework of
Scalar QED. These two processes are interesting not only for the technical
aspect of PHOTOS Monte Carlo, but also for precision measurement of
alpha_{QED}(M_Z), g-2, as well as pi pi scattering lengths.Comment: 6 pages, 11 figures, proceedings of the PhiPsi09, Oct. 13-16, 2009,
Beijing, Chin
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