Towards a systematic study of {D₁,D₂}-{D,D*} scattering and exotic vector states

Abstract

As one of the four known fundamental forces in nature, the strong interaction is crucial for the formation of matter. Established in the early 1970s, the underlying field theory of quantum chromodynamics is embedded in our current Standard Model of particle physics, describing the strong interaction between quarks and gluons. However, due to its non-perturbative nature at low momentum transfer, we nowadays face a wide range of phenomena that still need to be understood. <br /> Especially in recent years, various collider experiments reported numerous states that show properties inconsistent with quark-model predictions. So far there exists not only significant tension between the parameters extracted from different exclusive measurements for these so-called exotic states, but there is in some cases even no consensus on the actual number of states that contribute. One reason for this is that the experimental data are analyzed for the channels individually and parameterized by a simple sum of Breit-Wigner functions - in particular omitting relevant threshold effects. In this work, we aim towards a systematic study of the vector states above .2 , text{GeV}$, consistent with the principles of analyticity and unitarity. <br /> The first chapter introduces the theoretical framework relevant to our analyses. In the second chapter, we present our initial study of the energy range from .2$ to .35 , text{GeV}$, which hosts most predominantly the $Y(4230)$. New data published in 2022 and 2023 clearly highlight the asymmetric lineshape in $jpsi pi^+ pi^-$ at the $D_1 bar D$ threshold. We demonstrate that the experimental data of eight final states are consistent with the assumption that the $Y(4230)$ is a $D_1 bar D$ hadronic molecule. This is achieved by including interference with the well-known conventional charmonium state $psi(4160)$, as well as taking the relevant thresholds into account.medskip <br /> In the third chapter we lay the foundation to significantly extend the studied energy range. While our first analysis focused solely on the intermediate $D_1 bar D$ channel, heavy quark spin symmetry also calls for potential bound states in $D_1 bar D^*$ and $D_2 bar D^*$. We present the necessary formalism for the future study of the full coupled channel dynamics.