Away-side azimuthal distribution in a Markovian parton scattering model

An event generator is constructed on the basis of a model of multiple scattering of partons so that the trajectory of a parton traversing a dense and expanding medium can be tracked. The parameters in the code are adjusted to fit the Δϕ azimuthal distribution on the far side when the trigger momentum is in the nonperturbative region, p_T^trigger<4 GeV/c. The dip-bump structure for 1<p_T^assoc<2.5 GeV/c is reproduced by averaging over the exit tracks of deflected jets. An essential characteristic of the model, called Markovian Parton Scattering (MPS) model, is that the scattering angle is randomly selected in the forward cone at every step of a trajectory that is divided into many discrete steps in a semiclassical approximation of the nonperturbative scattering process. Energy loss to the medium is converted to thermal partons, which hadronize by recombination to give rise to the pedestal under the bumps. When extended to high trigger momentum with p_T^trigger>8 GeV/c, the model reproduces the single-peak structure observed by STAR without the need to invoke any new dynamical mechanisms.