New results on e+e--line emission in U+Ta collisions ORANGE collaboration at GSI
Date
1997Author
Leinberger, U.Berdermann, E.
Heine, F.
Heinz, S.
Joeres, O.
Kienle, P.
Koenig, I.
Koenig, W.
Kozhuharov, C.
Rhein, M.
Schröter, A.
Tsertos, Haralambos
Source
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy PhysicsVolume
394Issue
1-2Pages
16-22Google Scholar check
Metadata
Show full item recordAbstract
We present new results obtained from a series of follow-up e+e--coincidence measurements in heavy-ion collisions, utilizing an improved experimental set-up at the double-Orange β-spectrometer of GSI. The collision system 238U + 181Ta was reinvestigated in three independent runs at beam energies in the range (6.0-6.4) × AMeV and different target thicknesses, with the objective to reproduce a narrow sum-energy e+e--line at ∼635keV observed previously in this collision system. At improved statistical accuracy, the line could not be found in these new data. For the "fission" scenario, an upper limit (1σ) on its production probability per collision of 1.3 × 10-8 can be set which has to be compared to the previously reported value of [4.9 ± 0.8(stat.) ± 1.0(syst.)] × 10-7. Based on the new results, a reanalysis of the old data shows that the continuous part of the spectrum at the line position is significantly higher than previously assumed, thus reducing the production probability of the line by a factor of two and its statistical significance to ≤ 3.4σ.