WIDG Seminar: Zoltan Varga, Wigner Research Centre for Physics, “Investigating the role of the underlying event in the charm-baryon enhancement”

The factorization hypothesis states that the production cross-section of heavy-flavor hadrons can be calculated as the convolution of three independent terms: the parton distribution function of the colliding hadrons, the production cross sections of the heavy-quarks in the hard partonic process, and finally the fragmentation functions of the heavy-flavor quarks into the given heavy-flavor hadron species. The fragmentation function has been traditionally treated as universal, i.e. independent of the collision systems.
Recent charmed-baryon measurements by ALICE and CMS show a low-momentum enhancement over model predictions based on e+e− collisions, which challenges this traditional assumption. One of the latest measurements also shows that this enhancement depends on the final-state multiplicity of the collision event. Several scenarios have been proposed to explain the emerging pattern, including string formation beyond leading order, the so-called enhanced color re-connection, which provides a qualitatively correct description of these findings for pp collisions.
In our contribution, we investigated the charm-baryon enhancement with PYTHIA 8 Monte-Carlo generator and enhanced color-reconnection models. We proposed a method based on several event-activity classifiers to identify the source of the charm-baryon enhancement. We conclude that, within the scenario under investigation, the excess Λc production is connected to the underlying event and not to the jet production. We also present studies with several charmed-baryon species that address the role of the quark content and isospin state and allow for the comparison of charm and strange-baryon enhancement mechanisms.
These observables will provide a unique opportunity in the upcoming measurements of the high-luminosity LHC Run3 phase to have a better understanding of the charm fragmentation mechanisms, and will serve as a valuable tool for further model development.
Host: Sierra Weyhmiller, sierra.weyhmiller@yale.edu