Impact of the energy loss spatial profile and shear viscosity to entropy   density ratio for the Mach cone vs. head shock signals produced by a fast   moving parton in a quark-gluon plasma
  We compute the energy and momentum deposited by a fast moving parton in a quark-gluon plasma using linear viscous hydrodynamics with an energy loss per unit length profile proportional to the path length and with different values of the shear viscosity to entropy density ratio. We show that when varying these parameters, the transverse modes still dominate over the longitudinal ones and thus energy and momentum is preferentially deposited along the head-shock, as in the case of a constant energy loss per unit length profile and the lowest value for the shear viscosity to entropy density ratio. 
Alejandro Ayala, Jorge David Castano-Yepes, Isabel Dominguez and Maria   Elena Tejeda-Yeomans
hep-ph nucl-th