Coupled Boltzmann Transport Equations of Heavy Quarks and Quarkonia in Quark-Gluon Plasma

Abstract

We develop a framework of coupled transport equations for open heavy flavor and quarkonium states, in order to describe their transport inside the quark-gluon plasma. Our framework is capable of studying simultaneously both open and hidden heavy flavor observables in heavy-ion collision experiments and can account for both, uncorrelated and correlated recombination. Our recombination implementation depends on real-time open heavy quark and antiquark distributions. We carry out consistency tests to show how the interplay among open heavy flavor transport, quarkonium dissociation and recombination drives the system to equilibrium. We then apply our framework to study bottomonium production in heavy-ion collisions. We include ${\rm Y}(1S)$, ${\rm Y}(2S)$, ${\rm Y}(3S)$, ${\chi }_b(1P)$ and ${\chi }_b(2P)$ in the framework and take feed-down contributions during the hadronic gas stage into account. Cold nuclear matter effects are included by using nuclear parton distribution functions for the initial primordial heavy flavor production. A calibrated $2+1$ dimensional viscous hydrodynamics is used to describe the bulk QCD medium. We calculate both the nuclear modification factor $R_{\mathrm{AA}}$ of all bottomonia states and the azimuthal angular anisotropy coefficient $v_2$ of the ${\rm Y}(1S)$ state and find that our results agree reasonably with experimental measurements. Our calculations indicate that correlated cross-talk recombination is an important production mechanism of bottomonium in current heavy-ion experiments. The importance of correlated recombination can be tested experimentally by measuring the ratio of $R_{\mathrm{AA}}({\chi }_b(1P))$ and $R_{\mathrm{AA}}({\rm Y}(2S))$.

Comments: 36 pages, 7 figures, 3 tables; v2: changed to JHEP format, added a few references; v3: uncertainty analysis added, new measurement proposal to test correlated recombination; v4: minor change in Fig.7c and relevant discussions; v5: published version; link to the major part of the code: https://github.com/4KColo/Quarkonium_cython