Anomalous strong interaction shifts and widths of the 3d state in pionic Pt and Au

doi:10.1016/0370-2693(84)92048-3

Physics Letters B

Volume 136, Issues 1–2, 23 February 1984, Pages 24-28

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Abstract

The poinic 4f → 3d X-ray transitions in Pt and Au have been observed. The strong interaction monopole shifts ϵ_o and widths Γ_o of the 4f and 3dd levels have been deduced. For the pionic 4f levels standard optical potentials predict the experimental values quite well, whereas the deeper bound 3d states have shifts and widths that are smaller by a factor of about two than the theoretical predictions.

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A theoretical approach to pionic atoms and the problem of anomalies
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We have constructed a theoretical optical potential for pionic atoms based on the first- and second-order terms of a many-body expansion on the number of ph excitations. The p-wave parts are very much influenced by the medium polarization. The quenching at large densities produced by this phenomenon, together with the one from the Lorentz-Lorenz effect, and modifications over standard potentials due to the isospin dependence, lead to a new potential which produces notoriously improved results in the problem of anomalies. A clearer definition of this problem is proposed as the inability of standard potentials to reproduce simultaneously the data for light and heavy nuclei. Finally a semiphenomenological potential is obtained by adding some small terms to the theoretical potential which are fitted to the data and by means of which a good overall fit to the data is obtained. This potential is then used to make predictions for energies and widths of deeply bound pionic states so far unobserved.
An improved parametrization of the optical potential for pionic atoms
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We try to find an improved phenomenological optical potential for pionic atoms in two steps. First, we perform a new fit of the parameters in the standard optical potentials by using a large data base of 140 pionic atom data. A χ² is obtained that is substantially lower than with any previous parameter set. In a second step, we extend the number of parameters by using a more general form for the terms quadratic in the nuclear density. This extended version yields a reduction of the χ² by about a factor of two. The new fit includes a good description of shifts and widths of the deeply bound 3d orbits in heavy nuclei such as ¹⁸¹Ta, ^natRe, ^natPt, ¹⁹⁷Au, ²⁰⁸Pb and ²⁰⁹Bi. The value of the additional parameters in the extended version are difficult to interpret in the context of the chosen form of the optical potential and indicate that higher-order effects play a role.
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Meson exchange in nuclei and the EMC effect
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^☆: This work is part of the research programme of NIKHEF-K at Amsterdam, made possible by financial support from the Foundation for Fundamental Research on Matter (FOM) and the Netherlands' Organization for the Advancement of Pure Research (ZWO).

^∗: The authors are grateful to the CERN staff, especially to Dr. B.W. Allardyce and his crew, for putting at our disposal the SC muon channel for trial experiments during the summer of 1982. We also want to acknowledge the valuable contribution of Ir.J.G. Kromme, Interuniversity Reactor Institute, Delft, in the development of the CAMAC-driver and parts of the real time program.

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Physics Letters B

Abstract

References (14)

Nucl. Phys.

Nucl. Phys.

Nucl. Phys.

Nucl. Phys.

Nucl. Phys.

Phys. Lett.

Nucl. Phys.

Cited by (17)

A theoretical approach to pionic atoms and the problem of anomalies

An improved parametrization of the optical potential for pionic atoms

Pion absorption in light nuclei

Inclusive radiative pion capture in nuclei

Meson exchange in nuclei and the EMC effect

Scattering of low energy pions by <sup>12</sup>C, <sup>40</sup>Ca, <sup>58,60,64</sup>Ni and the anomaly in pionic atoms

Anomalous strong interaction shifts and widths of the 3d state in pionic Pt and Au☆

Abstract

Nucl. Phys.

Nucl. Phys.

Nucl. Phys.

Nucl. Phys.

Nucl. Phys.

Phys. Lett.

Nucl. Phys.