Background-free signal of a jet-induced diffusion wake in quark-gluon plasma

Rapidity asymmetry of jet-hadron correlation has been proposed as a robust signal of dijet‐induced diffusion wake in quark-gluon plasma in high‐energy heavy-ion collisions. We generalize this observable to other jet configurations such as γ / Z 0 jets and propose a new method to compute the rapidity asymmetry that is free of background. In this new method, the rapidity of the trigger is fixed or restricted to a symmetrical range while the rapidity of the associated jet is varied. The rapidity asymmetry is defined as the difference between the hadron rapidity distribution in the opposite azimuthal direction of the jet (or the same direction of the trigger) with different associated jet rapidities. Since the background in this hadron rapidity distribution with different associated jet rapidity is identical, it will be completely canceled in the rapidity asymmetry. Such background-free rapidity asymmetry caused by jet-induced diffusion wake is demonstrated in CoLBT-hydro simulations of dijets and γ -jets in Pb + Pb collisions at the CERN Large Hadron Collider, which weakens as hadron p T increases, and subtraction of a p + p baseline has a negligible effect.