THE ODYSSEY OF KAONIC ATOMS STUDIES AT THE DAΦNE COLLIDER: FROM DEAR TO SIDDHARTA-2

In this paper, an overview of kaonic atoms studies from the late 90s to nowadays at the DAΦNE collider at INFN-LNF is presented. Experiments on kaonic atoms are an important tool to test and optimize phenomenological models on the low-energy strong interaction. Since its construction, the DAΦNE collider has represented an ideal machine to perform kaonic atoms measurements, thanks to the unique beam of kaons coming from the ϕs produced in the collider decays. The DEAR and SIDDHARTA experiments achieved the precise evaluation of the shift and width of the 2p → 1s transition in kaonic hydrogen due to the strong interaction, and thus provided a measurement strictly linked to isospin-dependent antikaon–nucleon scattering lengths. To fully disentangle the iso-scalar and iso-vector scattering lengths, the measurement of kaonic deuterium is necessary as well. The SIDDHARTA-2 experiment is now taking data at the DAΦNE collider with the aim to fulfill the need of this measurement, and therefore provide important information to the various phenomenological models on low-energy strong interactions with strangeness. The SIDDHARTA-2 Collaboration is also exploring the possibility to perform future kaonic atoms experiments, developing X-ray detector systems beyond the current state-of-art. These measurements are crucial for a deeper understanding of the kaon interactions with nuclei and for solving the kaon mass “puzzle”.