The KˉN system at threshold is a sensitive testing ground for low energy QCD, especially for the explicit chiral symmetry breaking. Therefore, we have measured the K-series x rays of kaonic hydrogen atoms at the DAΦNE electron-positron collider of Laboratori Nazionali di Frascati, and have determined the most precise values of the strong-interaction energy-level shift and width of the 1s atomic state. As x-ray detectors, we used large-area silicon drift detectors having excellent energy and timing resolution, which were developed especially for the SIDDHARTA experiment. The shift and width were determined to be ϵ1s=−283±36±6(syst) eV and Γ1s=541±89(stat)±22(syst) eV, respectively. The new values will provide vital constraints on the theoretical description of the low-energy KˉN interaction.
@article{arxiv.1105.3090,
title = {A New Measurement of Kaonic Hydrogen X rays},
author = {M. Bazzi and G. Beer and L. Bombelli and A. M. Bragadireanu and M. Cargnelli and G. Corradi and C. Curceanu and A. d'Uffizi and C. Fiorini and T. Frizzi and F. Ghio and B. Girolami and C. Guaraldo and R. S. Hayano and M. Iliescu and T. Ishiwatari and M. Iwasaki and P. Kienle and P. Levi Sandri and A. Longoni and V. Lucherini and J. Marton and S. Okada and D. Pietreanu and T. Ponta and A. Rizzo and A. Romero Vidal and A. Scordo and H. Shi and D. L. Sirghi and F. Sirghi and H. Tatsuno and A. Tudorache and V. Tudorache and O. Vazquez Doce and E. Widmann and J. Zmeskal},
journal= {arXiv preprint arXiv:1105.3090},
year = {2011}
}