Charm and Bottom Hadrons in Hot Hadronic Matter

TL;DR

This paper reviews how charm and bottom hadrons interact within hot hadronic matter, emphasizing their role in understanding the medium created in heavy-ion collisions and highlighting recent theoretical and experimental developments.

Contribution

It provides a comprehensive review of interactions, scattering amplitudes, and transport properties of heavy-flavor hadrons in the hadronic phase, including new insights into bottom sector and excited states.

Findings

Rescattering effects significantly influence heavy-flavor observables.

Interactions are strongest near the QCD pseudo-critical temperature.

Transport calculations show notable impact on experimental measurements.

Abstract

Heavy quarks, and the hadrons containing them, are excellent probes of the QCD medium formed in high-energy heavy-ion collisions, as they provide essential information on the transport properties of the medium and how quarks color-neutralize into hadrons. Large theoretical and phenomenological efforts have been dedicated thus far to assess the diffusion of charm and bottom quarks in the quark-gluon plasma and their subsequent hadronization into heavy-flavor (HF) hadrons. However, the fireball formed in heavy-ion collisions also features an extended hadronic phase, and therefore any quantitative analysis of experimental observables needs to account for the rescattering of charm and bottom hadrons. This is further reinforced by the presence of a QCD cross-over transition and the notion that the interaction strength is maximal in the vicinity of the pseudo-critical temperature. We review existing approaches for evaluating the interactions of open HF hadrons in a hadronic heat bath and the pertinent results for scattering amplitudes, spectral functions and transport coefficients. While most of the work to date has focused on $D$-mesons, we also discuss excited states as well as HF baryons and the bottom sector. Both the HF hadro-chemistry and bottom observables will play a key role in future experimental measurements. We also conduct a survey of transport calculations in heavy-ion collisions that have included effects of hadronic HF diffusion and assess its impact on various observables.