摘要
Kaonic hydrogen atoms provide a unique laboratory to probe the kaon-nucleon strong interaction at the energy threshold, allowing an investigation of the interplay between spontaneous and explicit chiral symmetry breaking in low-energy QCD. The SIDDHARTA Collaboration has measured the m>Km>-series X rays of kaonic hydrogen atoms at the DA桅NE electron-positron collider of Laboratori Nazionali di Frascati, and has determined the most precise values of the strong-interaction induced shift and width of the 1m>sm> atomic energy level. This result provides vital constraints on the theoretical description of the low-energy interaction.