Bochum 1998 – scientific programme
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HK: Hadronen und Kerne
HK 5: Hadronic Probes I, Protons, Antiprotons, Pions
HK 5.3: Group Report
Monday, March 16, 1998, 15:00–15:30, C
Deeply bound pionic states and the effective π− mass in lead* — •H. Gilg2, H. Geissel1, A. Gillitzer2, R.S. Hayano3, J. Homolka2, K. Itahashi3, N. Iwasa1, P. Kienle2, M. Knülle2, M. Münch2, G. Münzenberg1, K. Oyama3, W. Schott4, and T. Yamazaki5 — 1Gesellschaft für Schwerionenforschung, D-64291 Darmstadt, Germany — 2Physik-Department E12, Technische Universität München, D-85748 Garching, Germany — 3Department of Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113, Japan — 4Physik-Department E18, Technische Universität München, D-85748 Garching, Germany — 5Institute of Particle and Nuclear Studies, High Energy Accelerator Research Organization, 3-2-1 Midori-cho, Tanashi, Tokyo 188, Japan
Recently the deeply bound pionic states (2p)π and (1s)π in 207Pb coupled to (p1/2, f5/2, p3/2)n−1 neutron hole states were discovered in an experiment performed at the GSI Fragment Separator [1]. Already in a first analysis the Q-value spectrum of the 208Pb(d,3He) reaction at Td=600MeV revealed a prominent peak at Q∼ −135.5MeV which could be attributed to the population of the (2p)π state. In the more strongly bound region a shoulder of this peak was seen at the predicted position of the (1s)π peak.
Meanwhile a more involved analysis of the data was performed, where various
corrections, such as for the time dependence of the beam energy, the
ion-optical aberrations of the FRS, and the long term shifts of the
FRS magnetic fields, were taken into account. Due to the considerably
improved instrumental resolution (δ Q ∼ 0.4MeV)
the binding energy of the (1s)π state could be determined
(Bπ(1s) = (7.1 ± 0.2)MeV) and
more precise
values for the binding energy and the width of the (2p)π state
(Bπ(2p) = (5.31 ± 0.09)MeV, Γπ(2p) < 0.6MeV) were obtained.
The (2p)π binding energy puts a constraint
on the so far poorly known local (s-wave) part of the π−-nucleus
optical potential which was determined to be V0 = (19.3 ± 2.7) MeV [2]
in the 207Pb nucleus.
[1] T. Yamazaki et al., Z. Phys. A355 (1996) 219
[2] T. Yamazaki et al., to be published in Phys. Lett B
*supported by BMBF (06TM365)