Speaker
Description
For heavy ion collisions in the TeV beam energy region, the large number of initial hard scatterings create a richly "doped" hot quark-gluon plasma containing many charm quarks/anti-quarks. This provides a uniquely "charming" environment for the massive production of heavy flavor exotic hadrons, with the notable examples of X(3872) and Tcc states, and possibly helps solve puzzles about their intrinsic structures, as demonstrated by recent theoretical studies. Furthermore, fresh experimental data have started to arrive from LHCb and CMS and indicate nontrivial partonic medium effects on their production, whereas a clear understanding of relevant mechanisms is lacking. This talk will report two exciting theoretical results along this direction. First, we demonstrate how heavy ion measurements could help decipher the exotic structure between two popular model configurations: a loose hadronic molecule or a compact tetraquark. It turns out the two different structures have rather different sensitivity to the fireball volume in heavy ion collisions. By scanning centrality and thus systematically tuning the fireball volume, our dynamical simulations have indeed found about 2-order-of-magnitude difference in the X(3872) yield and a markedly different centrality dependence between hadronic molecules and compact tetraquarks. This offers a novel approach for using fireball size as a “yardstick” to calibrate the size of X(3872) and thus distinguishing the two scenarios. More recently such study has also been extended to the newly observed doubly-charmed exotic states, with similar findings. Second, we propose a new mechanism for medium-assisted production of X(3872) and use state-of-the-art hydrodynamic simulations to show how this can help quantitatively explain the latest LHCb and CMS data for its yield dependence on multiplicities from pp to pA and AA collisions. [Refs: PRL126(2021)1,012301; PRD104(2021)11,L111502; arXiv:2302.03828] [Supported by NSF Grant No. PHY-2209183]
