L. Tauscher

High spin states and neutron multiplicities after pion capture in181Ta and209Bi

The absorption of stoppedπ− in181Ta and209Bi has been investigated by studying prompt and delayedγ-ray spectra. Absolute cross-sections for the yield of isotopes per capturedπ− in (π−, xn) reactions, as well as the relative probability of populating nuclear states of different spins have been measured for the hafnium and lead isotopes, respectively. A spin as high as 20 has been observed in the production of204Pb. The ground-state rotational bands of the hafnium isotopes are excited to spin values up to 16. Neutron multiplicities as large as 15 have been observed for both targets. A neutron multiplicity of ≃8 is most probable for both tantalum and bismuth targets.The strong interaction monopole energy shiftɛ0 and widthΓ0 for the 4f level are found to beε0(181Ta)=540±100eV; ɛ0(209Bi)=1790±150 eV;Γ0(181Ta)=225±57 eV;Γ0(209Bi) =1166±70 eV. The quadrupole moments, determined from the hyperfine splitting of the 4f pionic atom level, areQ=3.30±0.06b andQ=}-0.50±0.08b for181Ta and209Bi, respectively.

A New Effect in Pionic Atoms

Abstract We show that a likely explanation of the anomalous energy shifts in heavy pionic atoms is the energy dependence of the s-wave πN scattering amplitudes. This leads to an energy dependence of the π -nuclear optical potential. As a result, a non-trivial Coulomb term appears which leads to a remarkably better agreement with experiments without additional free parameters. An anomaly persists for the widths.

Pionic and muonic X-ray transitions in liquid helium

Abstract Energies and intensities of pionic and muonic X-rays in liquid 4 He have been measured with a Si (Li) detector. The energy shift due to strong interaction effects of the pionic 1s level in 4 He was determined to be −75.7±2.0 eV. The natural line width of this level is 45±3 eV. These values are compared with different theoretical predictions. Cascade calculations, including external Auger effect and sliding transitions, have been performed to reproduce the yields of the muonic and pionic transitions. The pionic 2p level width is deduced: Γ 2 p = (1.1 ± 0.5) × 10 12 sec −1 = (7.2±3.3) × 10 −4 eV .

Nuclear radii of light nuclei from muonic X-ray measurements

Abstract Measurements of the muonic 2p-1s transition energies in nuclei with Z ⩽ 17 are reported. Nuclear charge radii are deduced and compared with data from electron scattering.

An analysis of pion-nucleus scattering lengths within an α-cluster model

Abstract Pion-nucleus s-wave scattering lengths are calculated from a multiple scattering series in terms of the π-α scattering length. Agreement on the level of 10–20% with the values obtained from mesic-atom data is achieved for all nuclei with A ≦ 20. This lends weight to the speculation that pion absorption on light nuclei takes place primarily on α-particle substructures.

Pionic 2p level widths in light nuclei

Abstract The yields of muonic and pionic 2p-1s X-ray transitions are given for Be, 10 B. nat B and C. Pionic 2p populations are calculated, and the natural widths of the pionic 2p levels from Be to Na are deduced by comparison with X-ray transition rates calculated with realistic pion wave functions.

K- mass and K- polarizability from kaonic atoms.

Abstract The K − mass was determined from kaonic atomic X-rays from Au and Ba to be 493.691 ± 0.040 MeV. An upper limit for the polarizability of the K − was found to be 0.020 fm 3 at 90% confidence.

Intensities of mesonic 2p - 1s X-rays in N, 16O, 18O, F, and Na

Abstract The yields of pionic and muonic 2p-1s X-rays are given for N, 16 O, 18 O, F, and Na. The populations of the pionic 2p levels are determined and the natural widths are deduced.

Intensities and strong interaction attenuation of kaonic x-rays

Abstract Relative intensities of numerous kaonic X-ray transitions have been measured for the elements C,P,S, and C1, from which level widths due to the strong K-nucleus absorption have been determined. From these and earlier published data, optical potential parameters have been derived and possible consequences on the nuclear matter distribution are discussed.

Y∗ resonances and kaonic atoms

Abstract We study the role of the Y 0 ∗ and Y 1 ∗ resonances in kaonic 12 C and 32 S. Non-local effects due to propagation of the Y 0 ∗ are investigated together with the influence of possible changes in the Y 0 ∗ position and width. The most recent parametrizations of the K − N amplitude will be used. It is shown that the kaonic widths and shifts suggest systematically a repulsive shift and an increased width of the Y 0 ∗ inside a nucleus.