First Measurements at the Daphne Fi-Factory with the DEAR Experimental Setup

The relevant background for the DEAR experiment - low-energy Xrays and ionizing particles - present in the DEAR interaction region of the DAPHNE e^+e^- collider was inves-tigated using the first stage DEAR setup and CCD detectors. An extensive Monte Carlo simulation was performed for the present setup and beam conditions. Good quantitative agreement between measurements and simulation was achieved. This is a confirmation that, with respect to the expected background, which gives an important contribution to the statistical precision of the experiment, the configuration chosen to measure the strong interaction shift and width in kaonic hydrogen and kaonic deuterium can indeed reach the planned level of accuracy.