4,202 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
Systematics of parton-medium interaction from RHIC to LHC
Despite a wealth of experimental data for high-P_T processes in heavy-ion
collisions, discriminating between different models of hard parton-medium
interactions has been difficult. A key reason is that the pQCD parton spectrum
at RHIC is falling so steeply that distinguishing even a moderate shift in
parton energy from complete parton absorption is essentially impossible. In
essence, energy loss models are effectively only probed in the vicinity of zero
energy loss and, as a result, at RHIC energies only the pathlength dependence
of energy loss offers some discriminating power. At LHC however, this is no
longer the case: Due to the much flatter shape of the parton p_T spectra
originating from 2.76 AGeV collisions, the available data probe much deeper
into the model dynamics. A simultaneous fit of the nuclear suppression at both
RHIC and LHC energies thus has great potential for discriminating between
various models that yield equally good descriptions of RHIC data alone.Comment: Talk given at Quark Matter 2011, 22-28 May 2011, Annecy, Franc
Elastic energy loss with respect to the reaction plane in a Monte-Carlo model
We present a computation of nuclear modification factor with respect
to the reaction plane in Au+Au collisions at GeV, based on
a Monte-Carlo model of elastic energy loss of hard partons traversing the bulk
hydrodynamical medium created in ultrarelativistic heavy-ion collisions. We
find the incoherent nature of elastic energy loss incompatible with the
measured data.Comment: 5 pages, 2 figure
Fate of silver nanoparticles in constructed wetlands : a microcosm study
Nano-enabled materials are produced at growing volumes which increases the likelihood of nanoparticles being released into the environment. Constructed wetlands (CWs) are likely to receive wastewater containing nanoparticles leaching from products during usage. Therefore, we investigate the retention of silver nanoparticles (Ag-NPs) in microcosms simulating CWs treating domestic wastewater. The effects of aeration and organic matter content on the Ag-NP removal efficiencies are studied in particular. CWs remove most of the Ag (80-90%) and the largest fraction of Ag is found in/on the biofilm. Detailed electron microscopy analyses suggest that Ag-NPs are transformed into Ag2S in all microcosm experiments. The good correlation between total suspended solids (TSS) and the Ag concentration measured in the effluent indicates that Ag-NPs are bound to the solids in the effluent. Aeration of the microcosms does not affect the release of Ag-NPs from the systems but increasing organic matter leads to increased amounts of Ag passing the CWs, correlating with the increased release of TSS from the CWs. These results suggest that Ag-NPs are retained with the (suspended) solids in CWs and that the removal efficiency of TSS is an important factor determining the discharge of Ag-NPs from CWs
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