Modified dihadron fragmentation functions in hot and nuclear matter

Heavy-Flavour Jets in High-Energy Nuclear Collisions

Reconstructed jets initiated from heavy quarks provide a powerful tool to probe the properties of the quark–gluon plasma (QGP) and to explore the mass hierarchy of jet quenching. In this article, we review the recent theoretical progresses on heavy-flavour jets in high-energy nuclear collisions at the RHIC and LHC. We focus on the yields and substructures of charm and bottom quark jets with jet-quenching effects, such as the nuclear modification factors, transverse momentum imbalance, angular correlation, radial profiles, fragmentation functions, the “dead-cone” effect, etc.

Jet quenching and medium response in high-energy heavy-ion collisions: a review

Jet quenching has been used successfully as a hard probe to study properties of the quark-gluon plasma (QGP) in high-energy heavy-ion collisions at both the relativistic heavy-ion collider and the large hadron collider. We will review recent progresses in theoretical and phenomenological studies of jet quenching with jet transport models. Special emphasis is given to effects of jet-induced medium response on a wide variety of experimental observables and their implications on extracting transport properties of the QGP in heavy-ion collisions.

Dihadron fragmentation functions for large invariant mass

Using perturbative quantum chromodynamics, we compute dihadron fragmentation functions for a large invariant mass of the dihadron pair. The main focus is on the interference fragmentation function H(1)(∢), which plays an important role in spin physics of the nucleon. Our calculation also reveals that H(1)(∢) and the Collins fragmentation function have closely related underlying dynamics. By considering semi-inclusive deep-inelastic scattering, we further show that collinear factorization in terms of dihadron fragmentation functions and collinear factorization in terms of single-hadron fragmentation functions provide the same result in the region of intermediate invariant mass.

Perturbative QCD description of heavy and light flavor jet quenching

We present a successful description of the medium modification of light and heavy flavor jets within a perturbative-QCD-based approach. Only the couplings involving hard partons are assumed to be weak. The effect of the medium on a hard parton, per unit time, is encoded in terms of three nonperturbative, related transport coefficients which describe the transverse momentum squared gained, the elastic energy loss, and diffusion in elastic energy transfer. Scaling the transport coefficients with the temperature of the medium, we achieve a good description of the centrality dependence of the suppression and the azimuthal anisotropy of leading hadrons. Imposing additional constraints based on leading order (LO) hard thermal loop (HTL) effective theory leads to a worsening of the fit, implying the necessity of computing transport coefficients beyond LO HTL.

Energy and momentum deposited into a QCD medium by a jet shower

For a hard parton moving through a dense QCD medium, we compute self-consistently the energy loss and the fraction deposited into the medium due to showering and rescattering of the shower, assuming weak coupling between probe and medium. The same transport coefficients thus determine both the energy loss and its deposition into the medium. This allows a parameter free calculation of the latter once the former are computed or measured. We compute them for a weakly interacting medium. Assuming a short thermalization time for the deposited energy, we determine the medium's hydrodynamical response and obtain a conical pattern that is strongly enhanced by showering.