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HK: Physik der Hadronen und Kerne

HK 3: Electromagnetic and Hadronic Probes I

HK 3.1: Gruppenbericht

Montag, 8. März 2004, 15:45–16:15, B

Recent results from light pionic atoms — •D. Gotta¹, D.F. Anagnostopoulos², S. Biri³, G. Borchert¹, J.-P. Egger⁴, H. Fuhrmann⁵, A. Gruber⁵, M. Hennebach¹, A. Hirtl⁵, P. Indelicato⁶, Y.-W. Liu⁷, B. Manil⁶, V.E. Markushin⁷, N. Nelms⁸, P.A. Schmelzbach⁷, L.M. Simons⁷, M. Trassinelli⁶, A. Wells⁸, and J. Zmeskal⁵ — ¹IKP, FZ Jülich — ²Dept. of Mat. Sc., Univ. Ioannina, Greece — ³Nucl. Res. Inst., Hung. Academy of Sc., Debrecen — ⁴Univ. de Neuchâtel, Switzerland — ⁵IMEP, Österr. Akademie d. Wiss., Vienna — ⁶Lab. Kastler–Brossel, Univ. P. et M. Curie, Paris — ⁷PSI, Switzerland — ⁸Dept. of Phys. and Astr., Univ. of Leicester, England

Recent results from pionic–atom measurements are a new precise determination of the charged pion mass and of the hadronic effects in the ground–state of pionic hydrogen. The new value for the pion mass results from a simultaneous measurement of pionic nitrogen and muonic oxygen X–rays, the precison of which is given by statistics and the knowledge of the detector geometry. The experiment in pionic hydrogen profits from a significantly improved peak–to–background ratio and statistics. Moreover, three different transitions have been measured and the target density was varied over a pressure range of 200. This served to disentangle the effects of Coulomb de–excitation and constrain the hadronic width to lower values than obtained from previous experiments.