858 research outputs found
Collision Energy Evolution of Elliptic and Triangular Flow in a Hybrid Model
While the existence of a strongly interacting state of matter, known as
'quark-gluon plasma' (QGP), has been established in heavy ion collision
experiments in the past decade, the task remains to map out the transition from
the hadronic matter to the QGP. This is done by measuring the dependence of key
observables (such as particle suppression and elliptic flow) on the collision
energy of the heavy ions. This procedure, known as 'beam energy scan', has been
most recently performed at the Relativistic Heavy Ion Collider (RHIC).
Utilizing a Boltzmann+hydrodynamics hybrid model, we study the collision energy
dependence of initial state eccentricities and the final state elliptic and
triangular flow. This approach is well suited to investigate the relative
importance of hydrodynamics and hadron transport at different collision
energies.Comment: 6 pages, 6 figures. Talk given in CPOD 2013 - 8th International
Workshop on Critical Point and Onset of Deconfinement, March 11-15, Napa, C
Longitudinal flow and onset of deconfinement
The effects of the onset of deconfinement on longitudinal and transverse flow
are studied. First, we analyze longitudinal pion spectra from
GeV to GeV within Landau's hydrodynamical model and the
UrQMD transport approach. From the measured data on the widths of the pion
rapidity spectra, we extract the sound velocity in the early stage of
the reactions. It is found that the sound velocity has a local minimum
(indicating a softest point in the equation of state, EoS) at GeV. This softening of the EoS is compatible with the assumption of
the formation of a mixed phase at the onset of deconfinement. Furthermore, the
energy excitation function of elliptic flow () from MeV
to GeV is explored within the UrQMD framework and
discussed in the context of the available data. The transverse flow should also
be sensitive to changes in the equation of state. Therefore, the
underestimation of elliptic flow by the UrQMD model calculation above GeV might also be explained by assuming a phase transition from a
hadron gas to the quark gluon plasma around this energy. This would be
consistent with the model calculations, indicating a transition from hadronic
matter to ``string matter'' in this energy range.Comment: Proceedings of the 3rd International Workshop The Critical Point and
Onset of Deconfinement, Firenze, Ital
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