First results on kaonic hydrogen from the DEAR experiment

The objective of DEAR (DAPhiNE Exotic Atom Research) is the measurement of the K-alpha line shift and width, due to the strong interaction, in kaonic hydrogen and a similar measurement - the first one - in kaonic deuterium. The aim is a precision determination of the antikaon-nucleon isospin dependent scattering lengths in order to obtain the kaon nucleon sigma terms. In a first phase, dedicated to the calibration and optimization of the setup, the experiment collected data on kaonic nitrogen: for the first time a complex of three transitions (7-->6 at 4.6 keV, 6-->5 at 7.6 keV and 5-->4 at 14 keV) was measured, and the corresponding yields obtained. The kaonic hydrogen measurement was performed for a total integrated luminosity of about 60 pb(-1) in the last months of the 2002 year. Data analyses are in progress, preliminary results being hereby presented, together with those on kaonic nitrogen.