e+e- pairs from 238U + 206Pb collisions

S. Heinz; E. Berdermann; F. Heine; O. Joeres; P. Kienle; I. Koenig; W. Koenig; C. Kozhuharov; U. Leinberger; M. Rhein; A. Schroeter; H. Tsertos

arXiv · nucl-ex/9612006

e+e- pairs from 238U + 206Pb collisions

S. Heinz·E. Berdermann·F. Heine·O. Joeres·P. Kienle·I. Koenig·W. Koenig·C. Kozhuharov·U. Leinberger·M. Rhein·A. Schroeter·H. Tsertos

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Abstract

We present the results from e+e- coincidence measurements in 238U + 206Pb collisions at a beam energy of 5.93 MeV/u, using an improved experimental setup at the double-Orange spectrometer of GSI. The capability of our device to detect Internal-Pair-Conversion (IPC) e+e- pairs from discrete nuclear transitions of a moving emitter is demonstrated by investigating the known 1.844 MeV (E1) transition in 206Pb and the 1.770 MeV (M1) transition in 207Pb, excited via Coulomb excitation and a neutron transfer reaction, respectively. The Doppler-shift corrected e+- sum-energy spectra show weak lines at the expected energies with cross sections being consistent with the measured excitation cross sections of the corresponding $γ$ lines and the theoretically predicted IPC coefficients. No other e+e- sum-energy lines were found in the measured spectra. The observed transfer cross sections show a strong dependence on the distance of closest approach (R_min), thus signaling also a strong dependence on the bombarding energy close to the Coulomb barrier.

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S. Heinz, E. Berdermann, F. Heine, O. Joeres, P. Kienle, I. Koenig, W. Koenig, C. Kozhuharov, U. Leinberger, M. Rhein, A. Schroeter, H. Tsertos. 1996-12-29. e+e- pairs from 238U + 206Pb collisions. https://arxiv.org/abs/nucl-ex/9612006

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