Leading order, next-to-leading order, and non-perturbative parton collision kernels: effects in static and evolving media

Abstract

Energetic partons traveling in a strongly interacting medium lose energy by emitting radiation and through collisions with medium constituents. Non-perturbative, next-to-leading order and leading order collision kernels are implemented within AMY-McGill formalism. The resulting gluon emission rates are then evaluated and compared by considering scattering occurring in a brick of quark-gluon plasma, as well as in a realistic simulation of Pb + Pb collisions at √ s = 2.76 ATeV using martini.We find that the variations in quenching of hard partons resulting from using different kernels can be important, depending on the overall value of the strong coupling constant αs.

Jet medium modifications

“…While these advancements have significantly deepened our understanding of the in-medium emission process, their implications on jet quenching phenomenological analyses are yet to be fully explored. In fact, for some energy loss observables, the differences among various approaches might potentially be absorbed into the fitted values of free parameters [18], typically the jet transport coefficient q or the strong coupling α s , depending on the formalism. This is illustrated in figure 2, where we observe that for the 0 − 5% centrality class in √ s NN = 2.76 TeV Pb-Pb collisions, the curves representing different collision kernel models collapse onto each other and become indistinguishable when the strong coupling value is separately fitted to the charged hadron R AA data for each of them.…”

“…The left panel uses α s = 0.3 for the three curves, while the right panel uses fitted values of α s , yielding: α s = 0.28 (orange), α s = 0.24 (blue), and α s = 0.26 (red). Figure taken from [18], to which we refer the reader for further details. and transverse degrees of freedom are completely decoupled.…”

Hard Jet Substructure in a Multi-stage Approach

“…Thus, the main mechanism causing parton splittings changes dynamically in the medium. The evolution of such partons at lower virtuality but energy still large enough to treat the medium interaction perturbatively can be approximated by kinetic theorybased approaches for on-shell particles, as implemented by generators such as LBT [90,92,96,97], or MAR-TINI [84,111,113]. As partons transition to energies and virtualities close to those of the QGP, they begin to undergo strong coupling [89] and thermalization with the medium [117].…”