Precision Spectroscopy of Pionic Atoms From Pion Mass Evaluation to Tests of Chiral Perturb.pdfVIP

4 0 0 2 p Frascati Physics Series Vol. VVVVVV (xxxx), pp. 000-000 e DAΦNE 2004: Physics at meson factories – Frascati, June. 7-11 , 2004 S Selected Contribution in Plenary Session 4 1 ] h p - m o PRECISION SPECTROSCOPY OF PIONIC ATOMS: FROM t a PION MASS EVALUATION TO TESTS OF CHIRAL . s PERTURBATION THEORY c i Martino Trassinelli ∗ s y Laboratoire Kastler Brossel,Universit´e P. et M. Curie, F-75252 Paris, France h p [ 1 v 6 ABSTRACT 6 0 9 Preliminary results of the strong interaction shift and width in pionic 0 hydrogen (πH ) using an X-ray spectrometer with spherically bent crystals and 4 CCDs as X-ray detector are presented. In the experiment at the Paul Scherrer 0 Institute three different (np → 1s) transitions in πH were measured. Moreover / s the pion mass measurement using the (5 → 4) transitions in pionic nitrogen c and muonic oxygen is presented i s y h p 1 Introduction : v Pionic hydrogen atoms are unique systems to study the strong interaction at low i X energies 2). The influence of the strong interaction in pionic hydrogen can be r a ∗ On behalf of the PIONIC HYDROGEN and PION MASS collabora- tion 1) extracted from the (np → 1s) transitions. Compared to pure electromagnetic interaction, the 1s level is affected by an energy shift ǫ1s and a line broadening Γ1s . The shift and the broadening are related to the hadronic scattering lengths ah− − and ah− 0 , by the Deser-type formulae 3) : π p→π p π p→π n ǫ1s 1 h