New-EXOTICA: New Frontiers in Exotic Atoms: high-precision tests of QCD and QED and probes of beyond Standard Model physics

Exotic atoms—where electrons are replaced by heavier particles such as muons, pions, kaons, antiprotons or heavier antinuclei—serve as very powerful precision laboratories to investigate the fundamental interactions and symmetries of nature. By generating and measuring these atoms and their transitions, we are able to uniquely explore low-energy QCD effects through hadronic atoms, test strong-field QED, and, in very recent years, search for interactions that go beyond the Standard Model (BSM) and their carriers (dark bosons). The search of antinuclei in cosmic rays is also a possible way to detect BSM particles. Recent milestones in exotic atoms include the first-ever 2023-2024 measurement of the strong-interaction-induced energy shift and width in kaonic deuterium by the SIDDHARTA-2 collaboration, as well as highly accurate spectroscopic measurements of kaonic neon and test measurements of muonic atoms probing QED at field strengths approaching and exceeding the Schwinger limit. Studies of antiprotonic and pionic atoms in heavy nuclei are also setting new limits on possible fifth forces. The NEW-EXOTICA workshop aims to provide, for the first time, a unified platform for expert and young experimentalists and theorists from major universities and institutions working in the field and from major international facilities—including DAFNE, J-PARC, PSI, CERN-ELENA, and RIKEN—to share their latest findings, engage in deep discussions on theoretical frameworks, and define future paths for exotic atoms joint research.