Correlated e+ e− peaks observed in heavy-ion collisions

Salabura, P.; Backe, H.; Bethge, Κ.; Bokemeyer, H.; Cowan, T. E.; Folger, H.; Greenberg, Jay; Sakaguchi, Kaori; Schwalm, D.; Schweppe, John E.; Stiebing, K. E.

doi:10.1016/0370-2693(90)90126-q

Cited by 103 publications

(37 citation statements)

References 11 publications

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“…The decay in a bound state could change the angular correlation and also would show a positive shift in the AE = Ee+ -E e-energy-difference spectrum. Both have been observed experimentally, most clearly for the 750 keV line of the U-Ta-system [10]. Furthermore the invariant mass of the X ~ is reduced by the binding energy in dependence of the nuclear charge.…”

Section: Decay Of the Bound X ~mentioning

confidence: 65%

“…This has led to a large diversity of models and speculations on the nature of the object X ~ [9]. Meanwhile the situation has become even more complex since several line structures have been found which do not all confirm with the two-body decay scenario [10,11].In this paper we will briefly summarize the experimental situation (Sect. 2) and then concentrate on a particular model for a composite X ~ particle [12,13] which was devised to give a comprehensive description of the data (Sect.…”

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confidence: 99%

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Can extended objects explain the GSI e+ e? lines?

Stein

Graf

Reinhardt

et al. 1991

Z. Physik A - Hadrons and Nuclei

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The anomalous electron-positron coincidences observed in heavy-ion collisions have been interpreted as signal for the pair decay of hitherto unknown neutral objects with masses around 1.8 MeV. We discuss the decay modes of such extended composite particles when they are bound to a nucleus. In particular we investigate the angular correlation of the emitted pair and the competing single-photon decay channel. We confront the particle hypothesis with recent negative results from experiments searching for resonances in Bhabha scattering. The induced pair decay of a metastable 1 § § state in secondary collisions with target atoms is discussed as a possible explanation. PACS: 14.80.Pb; 12.90. +b; 23.20.Nx This is the characteristics of a two-body decay of a (slowly moving) particle-like object X~ § +e-with mass in the 1.8 MeV region. This has led to a large diversity of models and speculations on the nature of the object X ~ [9]. Meanwhile the situation has become even more complex since several line structures have been found which do not all confirm with the two-body decay scenario [10,11].In this paper we will briefly summarize the experimental situation (Sect. 2) and then concentrate on a particular model for a composite X ~ particle [12,13] which was devised to give a comprehensive description of the data (Sect. 3). In Sect. 4 we investigate the decay modes of X ~ bound to a nucleus. Section 5 confronts the particle hypothesis with recent data from Bhabha scattering experiments.

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Section: Decay Of the Bound X ~mentioning

confidence: 65%

mentioning

confidence: 99%

Can extended objects explain the GSI e+ e? lines?

Stein

Graf

Reinhardt

et al. 1991

Z. Physik A - Hadrons and Nuclei

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“…In follow-up extended e + e − -coincidence experiments electrons were measured in coincidence with positrons, and the measured e + e − -sum-energy spectra revealed even narrower lines [7][8][9][10]. First attempts were made to interpret these lines in the context of the e + e − -decay of a previously unknown neutral particle with a mass around 1.8 MeV/c 2 [7].…”

Section: Introductionmentioning

confidence: 99%

Positron spectra from internal pair conversion observed in 238U + 181Ta collisions

Heinz

Berdermann²,

Heine

et al. 2000

Eur Phys J A

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Abstract. We present new results from measurements and simulations of positron spectra, originating from 238 U + 181 Ta collisions at beam energies close to the Coulomb barrier. The measurements were performed using an improved experimental setup at the double-Orange spectrometer of GSI. Particular emphasis is put on the signature of positrons from Internal-Pair-Conversion (IPC) processes in the measured e + -energy spectra, following the de-excitation of electromagnetic transitions in the moving Ta

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“…However, e + e − -pairs emitted via IPC from heavy nuclei are of considerable interest, since IPC is the only known source of e + e − -pairs with a sharp sum energy. Narrow lines with sum energies (E Σ = E e + + E e − ) in the range 500 keV ≤ E Σ ≤ 800 keV have been found in heavy-ion experiments around the Coulomb barrier at GSI [15,16,17,18,19,20,21]. The angular correlation of the emitted leptons is of particular interest, since the response of the various setups depends strongly on it.…”

Section: Introductionmentioning

confidence: 99%