Dissertation at the Institute of Nuclear Physics on Exotic Mesons and Dispersive Formalism

July 20, 2022

We congratulate Dr. Daniel Alberto Stanischesk Molnar on completing his dissertation titled

"The Role of Exotic Mesons and Final State Interactions in e+e− Collisions"

In recent years, a plethora of new resonances has been discovered in the charmonium region, which cannot be interpreted in a simple quark model picture as states consisting of a charm quark and an anti-charm quark. A study of the reaction dynamics through which such states are produced is crucial to understanding the intrinsic properties of these exotic resonances and for shedding light on their nature. Daniel Molnar used a state-of-the-art approach to investigate three reactions in which charged exotic states were observed by the BESIII Collaboration in electron-positron collisions, achieved a physical description of the current experimental data, and furthermore made predictions to be tested in future experiments.

Short summary for scientists:

A powerful, non-perturbative method for analyzing hadronic processes is the dispersive formalism, which is based on the fundamental physical principles of causality, crossing symmetry, and unitarity of the S-matrix. In this work, this formalism is applied to study three reactions, e+e→ ψ(2S) π+π, e+e→ J/ψ π+π und e+e→ hc π+π in which charged exotic states have been observed by the BESIII collaboration. The exotic states are explicitly considered as intermediate states in the processes and the final state interaction (FSI) is included through a Muskelishvili-Omnès approach to provide a physical description of the experimental data.

As a result of this work, a new collaboration with the BESIII experiment started with the goal to apply the developed approach for the complete data sample and new measurements of the reactions e+e→ ψ(2S) π+π,  e+e→ J/ψ π+π,  e+e→ J/ψ K+K- und e+e→ hc π+π.  This will improve the determination of the masses, widths as well as the production and decay mechanism of the exotic resonances, therefore providing a better understanding of their nature.