Partonic transport approach for jet modification in the QGP

The quark-gluon plasma (()QGP()) is a unique state of matter created in high-energy nuclear collisions. QGP is filled with thermal excitation of color charges that are otherwise confined in hadrons in ordinary matter.

One of the key shreds of evidence of the existence of the QGP is that the production yield of high transverse momentum (()(p_T)()) hadrons and jets (()collimated spray of hadrons()) are strongly suppressed in nuclear collisions than the ‘‘naive’’ expectation scaled from proton-proton collisions. This phenomenon, known as ‘‘jet quenching’’ is understood as the result of the high-(p_T) partons (()quarks and gluons()) losing energy in a hot and dense color-deconfined medium.

We aim to reveal event more properties of the QGP using jet observables. For example, whether quarks and gluons behave as well-defined quasi-particle in the QGP, whether QGP continues to exist in collisions of smaller nuclei or at lower collision energies, etc. To answer these questions, one needs a flexible framework to test different assumptions on the way jets interact with the QGP and a good understanding of theoretical uncertainty to learn from experimental data.

We have developed the Linear Boltzmann plus Diffusion Model for Partonic Transport (()LIDO()) to study the evolution of energetic partons in the QGP. This model includes both the perturbative treatment of jet-medium collisions and the diffusion modeling for multiple-soft interactions The diffusion equation takes the soft transport coefficient as input, allowing for a flexible parameterization of the non-perturbative effect. Further, we implement the medium-induced parton radiation in a novel Monte-Carlo approach, which can be matched to theoretical calculations to next-to-leading-log order in certain limits. This new method significantly improves the accuracy of the LIDO model to test existing theoretical ideas.

Using the LIDO model, we have performed several studies on topics related to heavy meson production, quarkonia production, combined analysis of hadron and jet suppression, as well as modifications of internal structures of jets. In the most recent work, we have performed a first extraction of the jet transport parameter (\hat{q}) using both hadron and jet suppression data.