GSI Scientific report 1995

Amongst the research highlights, the first identification of the doubly magic nucleus "7"8Ni at the fragment separator and the mass measurements of unstable nuclei at the storage ring are particularly noteworthy. Following fragmentation of Au and Bi beams, respectively, a whole bunch of unstable nuclei could be simultaneously injected, stored and cooled in the storage ring. Using the method of Schottky frequency analysis, it was then possible to determine the masses of the different circulating isotopes with an accuracy of the order of 10"-"6. Employing this powerful technique, the masses of more than 280 isotopes could be measured in only two experimental runs. A number of other important results should at least be briefly mentioned: The measurement of the bound #beta#-decay of bare "1"8"7Re at the storage ring, which has astrophysical relevance, since in its neutral charge state, "1"8"7Re serves (besides "2"3"2Th and "2"3"8U) as a clock for the age of the universe; the new results obtained on kaon production and on kaon propagation at the Kaon-spectrometer and at the 4#pi#-detector, respectively, which indicate a change of the in-medium properties of kaons in dense hadronic matter; and last but not least the clarification of the e"+e"- puzzle, i.e. the origin of the e"+e"- lines observed more than ten years ago in very heavy collision systems at the UNILAC. With respect to the latter project, new data with very much improved statistics compared to the older runs were taken in 1994/95 by the EPOS and the Orange collaboration. In these new experiments, none of the lines observed earlier could be reproduced. Furthermore, it was shown by simulations that at least some of the structures seen before were most likely caused by statistical fluctuations. The clarification of the e"+e"- puzzle - although with a negative result - was urgently awaited by the whole community, and belongs beyond doubt to the most important results from recent UNILAC physics. The Annual Report contains many other - almost 180 - contributions with numerous results from nuclear and atomic physics, plasma physics, materials research, biophysics and also from accelerator technology and detector instrumentation. As in the years before, a reliable performance of the accelerators with more than 6000 hours of total operation time in 1995 has been a necessary prerequisite for all these results. The ongoing research programme, including the new projects - intensity upgrade, HADES and heavy-ion therapy - which are also addressed in the report, will ensure a leading role of GSI in the field of heavy ion research well beyond the year 2000. Several working groups with international membership have been established to investigate two major options, on one hand an energy increase for the heavy-ion/proton beam in combination with an electron beam, on the other a further intensity increase by several orders of magnitude. (orig./HK)Available from TIB Hannover: RA 3693(96-1) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman