New precision era of experiments on strong interaction with strangeness at DAFNE/LNF-INFN

The strong-interaction shifts and widths of kaonic hydrogen, deuterium, 3He, and 4He were measured in the SIDDHARTA experiment. The most precise values of the shift and width of the kaonic hydrogen 1s state were determined to be ϵ1s = −283 ± 36(stat)±6(syst) eV and Γ1s = 541±89(stat)±22(syst) eV. The upper limit of the kaonic deuterium Kα yield was found to be ≤ 0.39%. In addition, the shifts and widths of the kaonic 3He and 4He 2p states were determined to be ϵ2p(3He) = −2 ± 2(stat) ± 4(syst) eV and Γ2p(3He) = 6 ± 6(stat) ± 7(syst) eV; ϵ2p(4He) = +5 ± 3(stat) ± 4(syst) eV and Γ2p(4He) = 14 ± 8(stat) ± 5(syst) eV. These values are important for the constraints of the low-energy K¯N$\bar KN$ interaction in theoretical approaches.