arXiv subjects
Publications and source records attributed to Hannu Holopainen.
We develop an event-by-event ideal hydrodynamical framework where initial state density fluctuations are present and where we use a similar flow-analysis method as in the experiments to make a one-to-one $v_2$ comparison with the measured data. Our studies also show that the participant plane is quite a good approximation for the event plane.
Comparing four different (ideal and viscous) hydrodynamic models for the evolution of the medium created in 200 AGeV Au-Au collisions, combined with two different models for the path length dependence of parton energy loss, we study the effects of jet quenching on the emission-angle dependence of the nuclear suppression factor R_AA(phi) and the away-side per trigger yield I_AA(phi). Each hydrodynamic model was tuned to provide a reasonable description of the single-particle transverse momentum spectra for all collision centralities, and the energy loss models were adjusted to yield the same pion nuclear suppression factor in central Au-Au collisions. We find that the experimentally measured in-plane vs. out-of-plane spread in R_AA(phi) is better reproduced by models that shift the weight of the parton energy loss to later times along its path. Among the models studied here, this is best achieved by energy loss models that suppress energy loss at early times, combined with hydrodynamic models that delay the dilution of the medium density due to hydrodynamic expansion by viscous heating. We were unable to identify a clear tomographic benefit of a measurement of I_AA(phi) over that of R_AA(phi).
We present a computation of $π^0$ nuclear modification factor with respect to the reaction plane in Au+Au collisions at $\sqrt{s_{NN}}=200$ 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.