Theory of positron production in heavy-ion collisions

Reinhardt, Joachim; Müller, Berndt; Greiner, Walter

doi:10.1103/physreva.24.103

Cited by 204 publications

(153 citation statements)

References 90 publications

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“…8. In this description, atomic positron creation in supercritical heavy-ion collisions is found to originate from two processes which are "anschaulich" and formally well distinguished, but act coherently.…”

Section: Theoretical Frameworkmentioning

confidence: 99%

Positron production in crossed beams of bare uranium nuclei

et al. 1988

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Positron creation in crossed-beam collisions of high-energy, fully stripped heavy ions is investigated within the coupled-channel formalism. In comparison with fixed-target collisions of highly stripped heavy-ion projectiles positron production probabilities are enhanced by more than one order of magnitude. The increase results from the possibility to excite electrons from the negative energy continuum into all bound states. The positron spectrum is shifted towards higher energies because of the absence of electron screening. Rutherford scattering as well as nuclear collisions with time delay are investigated. We also discuss the filling of empty bound states by electrons from pair-production processes.

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Section: Theoretical Frameworkmentioning

confidence: 99%

Positron production in crossed beams of bare uranium nuclei

et al. 1988

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“…Consequently we end up with real electron-positron, e − e + , pairs. This effect of spontaneously emitted positrons is verified in experiment by collision of heavy nuclei, which when approaching each other create an effective field strong enough to let the lowest eigenvalue dive into the continuum (see [22]). …”

Section: Model the Free Dirac Operator Is Given Bymentioning

confidence: 76%

On the Vacuum Polarization Density Caused by an External Field

Hainzl

2004

Ann. Henri Poincaré

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Abstract. We consider an external potential, −λϕ, due to one or more nuclei. Following the Dirac picture such a potential polarizes the vacuum. The polarization density, ρ λ vac , as derived in physics literature, after a well known renormalization procedure, depends decisively on the strength of λ. For small λ, more precisely as long as the lowest eigenvalue, e 1 (λ), of the corresponding Dirac operator stays in the gap of the essential spectrum, the integral over the density ρ λ vac vanishes. In other words the vacuum stays neutral. But as soon as e 1 (λ) dives into the lower continuum the vacuum gets spontaneously charged with charge 2e. Global charge conservation implies that two positrons were emitted out of the vacuum, this is, a large enough external potential can produce electron-positron pairs.We give a rigorous proof of that phenomenon.

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“…These make the use of exact two-center eigenstates awkward for practical computations. It is then more convenient (Reinhardt et al 1981a) to project a quasibound state $ R (r,R), which approximates the resonance due to the dived state, out of the positron energy continuum and to orthogonalize this continuum with respect to this quasibound state, yielding modified positron states $g (r",R). Instead of the two-center eigenstates, one then uses this projected basis for negative electron energies.…”

Section: Basis Expansionmentioning

confidence: 99%

Quantum Mechanical Theory of Positron Production in Heavy Ion Collisions with Nuclear Contact

Heinz

1987

Physics of Strong Fields

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SEf' 2 < !98t: ABSTRACTThe interplay between atomic and nuclear interactions in heavy ion collisions with nuclear contact is studied. The general theoretical description is outlined and analyzed in a number of different limits (semiclassical approximation, DWBA, fully quantal description). The two most important physical mechanisms for generating atomic-nuclear interference, i.e., energy conservation and the introduction of additional phase shifts by nuclear reactions, are extracted. The resulting typical coupling matrix elements are analyzed for their relative importance in atomic and nuclear excitations. The description of nuclear influence on atomic excitations in terms of a classical time delay caused by nuclear reactions is reviewed, and its relationship to the underlying quantal character of the nuclear reaction is discussed.The theory is applied to spontaneous positron emission in supercritical heavy-ion collisions (Z tot £ 173). It is shown that nuclear contact can lead to line structures in the positron energy spectra if the probability distribution for nuclear delay times caused by the contact has contributions for T c 10~ sec. We explicitly evaluate a model where a pocket in the internuclear potential near the touching configuration leads to formation of nuclear molecules, and predict a resonance-like excitation function for the positron peak.Invited talk presented at NATO Advanced Summer Institute PHYSICS OF STRONG FIELDS Maratea, Italy June 1 -14, 1986 This manuscript has been authored under contract DE-AC02-76CH00016 with the U.S. Department of Energy. Accordingly, the U. S. government retains a non-exclusive, royalty-free license to publish or reproduce the published form of this contribution, or allow others to do so, for U. S. government purposes. DISTRIBUTION OF THIS D'JCUMtNT & UNLIMITED -1 -QUANTUM MECHANICAL THEORY OF POSITRON PRODUCTION IN HEAVY ION COLLISIONS WITH NUCLEAR CONTACT Ulrich HeinzPhysics Department Brookhaven National Laboratory Upton, New York 11973, USA ABSTRACTThe interplay between atomic and nuclear interactions in heavy ion collisions with nuclear contact is studied. The general theoretical description is outlined and analyzed in a number of different limits (semiclassical approximation, DWBA, fully quantal description). The two most important .physical mechanisms for generating atomic-nuclear interference, i.e., energy conservation and the introduction of additional phase shifts by nuclear reactions, are extracted. The resulting typical coupling matrix elements are analyzed for their relative importance in atomic and nuclear excitations. The description of nuclear influence on atomic excitations in terms of a classical time delay caused by nuclear reactions is reviewed, and its relationship to the underlying quantal character of the nuclear reaction is discussed.The theory is applied to spontaneous positron emission in supercritical heavy-ion collisions (Z tot > 173). It is shown that nuclear contact can lead to line structures in the positron energy spectra if the pro...

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Theory of positron production in heavy-ion collisions

Cited by 204 publications

References 90 publications

Positron production in crossed beams of bare uranium nuclei

Positron production in crossed beams of bare uranium nuclei

On the Vacuum Polarization Density Caused by an External Field

Quantum Mechanical Theory of Positron Production in Heavy Ion Collisions with Nuclear Contact

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