Search for narrow sum-energy lines in electron-positron pair emission from heavy-ion collisions near the Coulomb barrier

Journal Article · Mon Oct 02 00:00:00 EDT 1995 · Physical Review Letters

DOI:https://doi.org/10.1103/PhysRevLett.75.2658· OSTI ID:118581

Ahmad, I; Austin, S M; Back, B B; Betts, R R; Calaprice, F P; Chan, K C; Chishti, A; Chowdhury, P; Conner, C; Dunford, R W; Fox, J D; Freedman, S J; Freer, M; Gazes, S B; Hallin, A L; Happ, T; Henderson, D; Kaloskamis, N I; Kashy, E; Kutschera, W ; Last, J; Lister, C J; Liu, M; Maier, M R; Mercer, D J; Mikolas, D; Perera, P A.A.; Rhein, M D; Roa, D E; Schiffer, J P; Trainor, T A; Wilt, P; Winfield, J S; Wolanski, M; Wolfs, F L.H.; Wuosmaa, A H; Xu, G; Young, A; Yurkon, J E ^[1]

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1. Physics Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States)

The first results are presented from a new experiment, APEX, designed to study the previously reported sharp lines in sum-energy spectra of positrons and electrons produced in collisions of very heavy ions. Data were collected for {sup 238}U+{sup 181}Ta at 5.95, 6.10, and 6.30 MeV/u and {sup 238}U+{sup 232}Th at 5.95 MeV/u. In none of our analyses is any evidence found for sharp sum-energy lines. For the specific case of the isolated decay of a neutral particle of mass 1.4--2.1 MeV/{ital c}{sup 2}, the upper limits on cross sections obtained from the present data are significantly less than the previously reported cross sections.

• OSTI ID: 118581
• Journal Information: Physical Review Letters, Journal Name: Physical Review Letters Journal Issue: 14 Vol. 75; ISSN 0031-9007; ISSN PRLTAO
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
COULOMB FIELD
CROSS SECTIONS
ELECTRONS
EMISSION
ENERGY SPECTRA
HEAVY ION REACTIONS
PAIR PRODUCTION
POSITRONS
TANTALUM 181 TARGET
THORIUM 232 TARGET
URANIUM 238 REACTIONS