Light parton energy loss in a hard-soft factorized approach
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Quark-gluon plasma is a deconfined state of quarks and gluons, which can be produced in heavy ion collisions. Highly energetic partons, which are generated at the early time of a heavy ion collision, propagate through the plasma and lose energy by interacting with the plasma. The energy loss of even very energetic partons can be affected by non-perturbative effects from the strongly-coupled plasma. Hard interactions --- those with large momentum transfer between the energetic parton and the plasma --- are expected to have smaller non-perturbative effects, or even be accessible perturbatively, as a consequence of the running of the QCD coupling. On the other hand, ``soft'' parton-plasma interactions with small momentum transfer are expected to suffer the largest non-perturbative effects.
A stochastic treatment of these soft interactions of energetic partons provides an alternative approach to account for non-perturbative effects --- an approach that is agnostic to the strongly- or weakly-coupled nature of the underlying deconfined plasma. The dynamical details of the large number of soft interactions are encoded in a small number of transport coefficients. From a practical point of view, a stochastic description of a large number of soft interactions can also be more efficient numerically than a rate-based approach.
We present the first numerical implementation of a hard-soft factorized parton energy loss model. We first test and validate this factorization of parton energy loss in the weak coupling regime for a static medium. We introduce a dimensionless scale to quantify the kinematic range for which soft interactions can be described accurately with a stochastic approach. We use this scale to discuss a hard-soft factorization model for a strongly-coupled quark-gluon plasma, relevant for phenomenological applications in heavy ion collisions.
We perform a systematic data-driven extraction of the light parton transport properties in a quark-gluon plasma based on the hard-soft factorized model. As in this model, the larger number of soft interactions are described stochastically in terms of a small number of transport coefficients, these soft transport coefficients can capture non-perturbative effects, agnostic to the strongly- or weakly-coupled nature of the underlying deconfined plasma.
We constrain the temperature dependence of these soft transport coefficients by performing a Bayesian model-to-data comparison with jet measurements from RHIC and LHC, allowing us to better understand the non-perturbative effects suffered by soft interactions in heavy ion collisions.
heavy ion collisions
parton energy loss
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