Report on MESON2021

Abstract

The 16th International Workshop on Meson Physics took place 17–20 May 2021 (Figure 1). The workshop has a long tradition and is organized every two years by the Institute of Physics of the Jagiellonian University, Forschungszentrum Juelich, Italian Institute for Nuclear Physics-Frascati National Laboratories (LNF) Frascati, and Institute of Nuclear Physics Polish Academy of Science. Due to the pandemic situation, the meeting was delayed one year and held on-line via the Zoom platform. The virtual format unfortunately prevented participants from enjoying the traditional longnight discussions after the conference sessions in the unique atmosphere of the old Kraków city. Nevertheless, more than 230 participants registered and participated in the plenary and three parallel sessions scheduled every day. The many excellent talks were selected in the tradition for this conference, which is to cover a broad scientific program rather than only focus on a specific topic. During the first two days, the production, properties, and structure of mesons composed of heavy and light quarks were widely discussed. In particular, the newly discovered exotic states were presented by experimentalists and interpreted by various theoretical approaches. Other aspects that were lively discussed were the interaction of mesons with mesons and baryons in vacuum and hot and dense matter investigated in heavy ion collisions at various energy scales from the Schwerionensynchrotron (SIS) at the Society for Heavy Ion Research to the Large Hadron Collider. The next two days were devoted to studies of nucleon structure, nucleon–antikaon, and hyperon–nucleon interactions. In particular, new results of precision experiments searching for a neutron dipole moment and new results of proton radius should be singled out. Presented results of experimental and theoretical studies of hyperon–nucleon correlation functions in heavy ion collisions reveal an exciting possibility to access the corresponding interaction potentials, which might have an important impact on the understanding of the nature of compact neutron stars and provide a strong link between hadron physics and astrophysics. The final session was concluded with a presentation of new exciting results of the g-2 experiment at Fermilab and mysterious signal of the new X17 particle claimed to be a candidate for a dark photon. It is of course not possible to list all the interesting topics discussed in the conference in this short report. All interested readers are invited to look into the talks, which are available on the conference web page (https:// meson.if.uj.edu.pl). Some presentations, with the permission of the speakers, were recorded and can be replayed by those registered to the conference. The next MESON conference is scheduled for 2023 in an “old good traditional mode” and the organizing team already cordially invites all those interested to join us in Cracow! Please stay tuned and watch the conference web page MESON Conference web page.