The DEAR experiment-first results on kaonic hydrogen

The goal of the DEAR (DA NE exotic atom research) experiment is the precise determination of the isospin dependent antikaon-nucleon scattering lengths. The experiment accurately the Kα line shift and broadening, due to the strong interaction, in kaonic hydrogen and, for the first time, in kaonic deuterium. A precision measurement of kaonic hydrogen tests chiral symmetry breaking in systems with strangeness. An initial analysis of the DEAR experiment yields a shift ε1s = −195 ± 45 eV and a width Γ1s = 250 ± 125 eV, which is more precise than the previous kaonic X-ray experiment KpX at KEK, and allows for the first time to disentangle the full pattern of the kaonic hydrogen K-series line Kα, Kβ and Kγ .