Speaker
Description
Hadrons are composite states of quarks and gluons bound by the strong interaction. Conventional hadrons include baryons, composed of three quarks, and mesons, composed of a quark–antiquark pair. Non-conventional hadrons, known as exotics, have more complex quark content. A prominent example is the pentaquark, consisting of four quarks and one antiquark. In recent years, the LHCb experiment has discovered several pentaquarks containing charm and anti-charm quarks, posing new challenges for our understanding of how quarks organize themselves inside hadrons.
Determining the internal structure of pentaquarks remains an open problem. One class of models describes pentaquarks as hadronic molecules—weakly bound, color-neutral baryon–meson systems. An alternative is the compact model, in which quarks form tightly bound colored clusters that act as effective building blocks. In this picture, a pentaquark consists of a diquark (two quarks) and a triquark (two quarks and an antiquark). Because both clusters carry color, the compact model predicts stronger binding, analogous to the quark–antiquark interaction in conventional mesons. This analogy has motivated the extension of successful meson potential models to the pentaquark sector.
A key limitation of such potential models is that the constituent triquark mass enters as an external input and must be estimated phenomenologically. An independent determination of this quantity is therefore essential for assessing the reliability of compact pentaquark models.
Quantum chromodynamics (QCD) sum rules provide a framework for relating QCD-level dynamics to hadronic properties and are well suited for this task. In this talk, I will present our work using QCD sum rules to determine the constituent mass of a triquark containing an anti-charm quark. We compare our results with values used in potential models and discuss the implications for the pentaquarks observed by LHCb. Finally, directions for future work will be outlined.
| Keyword-1 | Quantum Chromodynamics |
|---|---|
| Keyword-2 | Exotic hadrons |