Kaonic Hydrogen Measurement With Dear At Da Phi Ne

The DEAR (DA Phi NE Exotic Atom Research) experiment(1) measured the energy of Xrays emitted in the transitions to the ground states of kaonic hydrogen. The shift E and the width Gamma of the 1s state are sensitive quantities for tests of the current understanding of the low energy antikaon-nucleon interaction. We obtain epsilon(1s) = -193 +/- 37 (stat.) +/- 6 (syst.) and Gamma(1s) = 249 +/- 112 (stat.) +/- 30 (syst.).