On the systematics of positron production in elastic heavy ion collisions

Kramer, M. A.; Blank, Β.; Bozek, E.; Ditzel, E.; Kankeleit, E.; Klotz-Engmann, G.; Müntz, G.; Oeschler, H.; Rhein, M.

doi:10.1016/0370-2693(90)90157-2

Cited by 4 publications

(4 citation statements)

References 12 publications

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“…This result, which is in qualitative agreement with earlier lneasurements [3,32] as well as with recent results of the TORI group [52], clearly establishes the appearance of a new positron source in very heavy collision systems, apart from the experimentally verified nuclear positron background. The empirical Z,-dependence, observed within a rather broad range of collision systems, confirms theoretical calculations that have predicted a power law for the total cross sections of atomic positron emission at bombarding energies near the Coulomb barrier [53,5].…”

Section: Dependence On the United Nuclear Charge Z+supporting

confidence: 91%

“…3---*0 + (E3, 2.615 MeV) and 2 + ~0 + (E2, 4 MeV), respectively, and can, therefore, be determined directly and even more accurately compared to the other systems [16]. This is the only collision system available which allows for proving the positron quasi-atomic theory with sufficient accuracy (see also [52]. As shown in Fig.…”

Section: P(o*o*)=!i Dee+ (Ee +mentioning

confidence: 92%

“…Finally, a more distinct mismatch in the absolute values has been reported recently by the TORI group at bombarding energies above the Coulomb barrier. They found that the measured quasi-atomic positron spectrum, obtained from Pb + Pb collisions at 8.6 MeV/u, exceeds the calculated yield approximately by a factor of two [52]. For this significant discrepancy between theory and experiment, no explanation has been found up to now.…”

Section: The Scalh N Factor For the Theoretical Calculationsmentioning

confidence: 93%

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Systematic studies of positron production in heavy-ion collisions near the Coulomb barrier

Tsertos¹,

Berdermann²,

Bosch³

et al. 1992

Z. Physik A - Hadrons and Nuclei

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We present the results obtained from systematic studies of positron creation for a series of heavy-collision systems, with united charge Z,=Z I+Z 2 ranging from Z,= 164 (Pb+Pb) to Z,,= 184 (U+U) at bombarding energies close to the Coulomb barrier, using the Orangefl-spectrometer at GSI. For each collision system studied, the dominating continuous distributions due to quasiatomic and nuclear positron emission are determined accurately. This is essential in obtaining the characteristics of the still unexplained monoenergetic positron lines which appear in the energy range between 200 keV and 400 keV. Our results are compared with coupled-channels calculations for quasi-atomic positron creation. The latter describe quite well the global features of the measured spectra, but overestimate systematically their absolute values. From the comparison, a common normalization factor of about 0.75 can be established for the calculated spectra. In particular, the dependence on Z,, of the measured emission probabilities was found to follow a power law (ocZ,~95-+~), in fair agreement with the theoretical prediction.

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Section: Dependence On the United Nuclear Charge Z+supporting

confidence: 91%

Section: P(o*o*)=!i Dee+ (Ee +mentioning

confidence: 92%

Section: The Scalh N Factor For the Theoretical Calculationsmentioning

confidence: 93%

See 1 more Smart Citation

Systematic studies of positron production in heavy-ion collisions near the Coulomb barrier

Tsertos¹,

Berdermann²,

Bosch³

et al. 1992

Z. Physik A - Hadrons and Nuclei

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“…It has been shown that the measured positron spectra are well explained assuming that the high-energy part of the spectra contains predominantly E1 transitions whereas the low-energy part, which can be described by an exponential distribution, is caused by collective E2 transitions. This procedure is an established tool used for the determination of the atomic positron production probability in heavy-ion collisions [34,35]. Taking into account an admixture of magnetic dipole transitions (Ml) does not alter the result of the conversion procedure.…”

Section: Discussionmentioning

confidence: 99%

Elastoplasticity in dissipative heavy-ion collisions

et al. 1994

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The spectral distributions of b electrons emitted in dissipative heavy-ion collisions represent an established tool to study the time evolution of the collision process. Especially, the yield of high-energy b electrons, which are measured for the first time up to an energy of 8 Mev, reBects short time scales and ofFers a unique possibility to examine the short deceleration phase at the beginning of the collision, which takes place within a few 10 s. The b-electron spectra measured in dissipative collisions of Pb+Pb at an incident energy of 12 MeV/nucleon are compared with theoretical predictions using a coupled-channels formalism. The nuclear trajectories needed as input for the calculations are obtained from reaction models. Using nuclear trajectories calculated within the one-body dissipation model give a far too low yield of high-energy 8 electrons indicating that the deceleration predicted by this model is too slow. The new dissipative diabatic model, which takes into account a non-Markovian dissipation at the beginning of the collision and which ascribes elastoplastic properties to nuclear matter, is able to reproduce both the fast deceleration and the long nuclear contact time deduced from the experimental data. PACS number(s): 25.70.1 m

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Electron excitations in superheavy quasimolecules

Muller-Nehler¹,

Soff

1994

Physics Reports

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On the systematics of positron production in elastic heavy ion collisions

Cited by 4 publications

References 12 publications

Systematic studies of positron production in heavy-ion collisions near the Coulomb barrier

Systematic studies of positron production in heavy-ion collisions near the Coulomb barrier

Elastoplasticity in dissipative heavy-ion collisions

Electron excitations in superheavy quasimolecules

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