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, thus providing a uniquely "charming" environment for the massive production of heavy flavor exotic hadrons such as the $\chi_{c1}$ (also known as X(3872)), X(6900) and Tcc states. While such exotic states have been studied for decades in hadron physics, many questions about their basic properties and intrinsic structures (e.g. large hadron molecules versus compact tetraquarks) are not understood. High energy nuclear collisions show promise as a new test ground that has the potential to help resolve some of these challenges, with fresh experimental data from LHCb and CMS indicating nontrivial partonic medium effects on their production. As an example to demonstrate such opportunity, we report recent calculations of the yield of $\chi_{c1}$ state based on two popular models of its possible configurations: a loose hadronic molecule or a compact tetraquark. It turns out that 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 $\chi_{c1}$ 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 exotic hadrons and thus distinguishing the two scenarios. Lastly, the talk will discuss the ongoing progress in the recently formed ExoHad Topical Collaboration to integrate hadronic physics inputs with medium environment and examine exotic hadron properties both in quark-gluon phase and in hot hadron gas, which would be crucial for a successful program of studying their production in heavy ion collisions.
| Category | Theory |
|---|---|
| Collaboration (if applicable) | ExoHad Collaboration |
