Hadronic molecules with heavy meson loops

C. Hanhart (FZJ) / Q.Wang (UB) / Q. Zhao (IHEP)

Since 2003, when the discovery of the X(3872) started a new era of hadron spectroscopy, many
socalled exotic states were found experimentally that show properties grossly at odds with those
predicted by the until then extremely successful quark model, which worked especially well in the
heavy quark sector. Most of these are located close to a threshold of two narrow hadrons. This
suggests that these states might be hadronic molecules — bound states of the mentioned hadron
pair similar to atomic nuclei being made of protons and neutrons. The main goal of this project is to
systematically map out the implications of the hypothesis that most of those exotic states are
predominantly of a molecular nature. In the third funding period we plan to work on a consistent
picture for molecule candidates and threshold phenomena simultaneously. This implies a
significant extension of the methods used previously, extending our investigations to the
pentaquarks observed by LHCb.