G. Backenstoss

Nuclear γ-rays following muon capture

Abstract The identification of the nuclear γ-rays that occur when muon capture leads to excited nuclei made it possible to evaluate the distribution of excited nuclei formed after the capture process. Mono-isotopic elements were used as targets, and γ-ray spectra were recorded using Ge(Li) detectors. In most cases the observed γ-rays accounted for a high fraction of the capture process. It could be concluded that the probability of zero neutron emission after muon capture was less than 5 % contrary to the findings of Kaplan and the predictions of Singer. The chance of single neutron emission was highest, about 50 %, and it dropped with increasing neutron multiplicity. The probability of forming a particular excited state in an isotope was in general about proportional to the spin, and about inversely proportional to the energy of the state.

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.

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.

STRONG INTERACTION SHIFTS AND WIDTHS IN LIGHT KAONIC ATOMS.

Abstract Energy shifts and line widths of X-ray transitions in kaonic atoms have been measured with an accuracy of about 10%. These data have been interpreted in terms of an optical potential. Whereas earlier approaches based on the free K − N scattering lengths fail to reproduce the data, a set of effective parameters consistant with all now available experiments could be derived.

OBSERVATION OF ANTIPROTONIC ATOMS.

Abstract X-rays originating from the antiprotonic cascade have been observed for several elements. From the energies of the measured antiprotonic transitions of 81Tl, the mass of the antiproton could be determined to ve 938.3±0.5 MeV. With this result the masses of the antiproton and the proton are equal within 0.5 MeV with a confidence of 68%. The magnetic moment of the antiproton shows up in a broadening of the n = 10 → n = 9 transition.

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.

Precision determination of the strong interaction shifts and widths of the 1s level in pionic 6Li, 7Li, and 9Be

The strong-interaction shifts of the 1s level in pionic 6Li, 7/Li, and 9Be were determined with an accuracy of better than 1%. The corresponding widths were determined with an accuracy of better than 6%. Significant deviations from the theory are observed as far as the absolute values as well as the systematics of the isospin dependence are concerned.