On the calculation of charge-exchange effects in a relativistic model for (γ n) reactions

2001 ◽  
Vol 79 (10) ◽  
pp. 1223-1230
Author(s):  
G M Lotz ◽  
H S Sherif
Keyword(s):  
Charge Exchange ◽  
Cross Sections ◽  
Mean Field ◽  
Transition Amplitude ◽  
Wave Functions ◽  
Meson Exchange ◽  
Relativistic Model ◽  
Exchange Contribution ◽  
Charge Exchange Reaction ◽  
Exchange Effects

The charge-exchange contribution to photoneutron emission is calculated in a relativistic model. The emission is regarded as a two-step process consisting of a direct electromagnetic knockout of a proton followed by a (p,n) charge-exchange reaction. The latter step is effected by the isovector components of the scalar and vector mean field optical potentials. A novel procedure, in which the pertinent integral is reduced to a simpler integral in combination with a differential equation, is adopted to evaluatethe transition amplitude. We find that the charge-exchange contribution is comparable in magnitude to the direct contribution over a range of photon energies. There is some dependence on the optical and binding potentials used to calculate nucleon wave functions. As expected, the sum of direct and charge-exchange contributions is not sufficient to account for the observed cross sections, confirming the importance of including meson exchange and isobar currents. PACS Nos.: 25.20Lj, 25.40Kv, 24.10Jv

Gamow–Teller strength functions from scattering experiments

1987 ◽  
Vol 65 (6) ◽  
pp. 691-698 ◽  
Author(s):  
O. Häusser
Keyword(s):  
Shell Model ◽  
Cross Sections ◽  
Mean Field ◽  
Wave Functions ◽  
Structure Information ◽  
Model Wave ◽  
Spin Flip ◽  
Strength Functions ◽  
Gamow Teller ◽  
Good Agreement

We present here recent [Formula: see text] results from TRIUMF that are relevant to the determination of spin-flip isovector strength functions in nuclei. Distortion factors needed for the extraction of nuclear-structure information have been deduced from cross sections and analyzing powers in elastic scattering for several energies and targets. Nonrelativistic optical potentials obtained by folding effective nucleon (N)–nucleus interactions with nuclear densities are found to overpredict both elastic and reaction cross sections, whereas Dirac calculations that include Pauli blocking are in good agreement with the data. Spin observables (Snn and Ay) for the quasi-elastic region in 54Fe[Formula: see text] at 290 MeV provide some evidence for the reduction of the effective proton mass predicted in relativistic mean-field theories as a consequence of the attractive scalar field in the nuclear medium. The energy dependence of the effective N–nucleus interaction at small momentum transfers has been investigated using isoscalar and isovector 1+ states in 28Si as probe states. We find that the cross sections for the isovector transitions are in good agreement with predictions for the dominant Vστ part of the Franey–Love interaction. Gamow–Teller (GT) strength functions have been obtained in 24Mg and 54Fe from measurements of both cross sections and spin–flip probabilities Snn. The spin-flip cross sections σSnn are particularly useful in heavier nuclei to discriminate against a continuous background of ΔS = 0 excitations. In the (s, d) shell where full shell-model wave functions are available, the GT quenching factors [Formula: see text] are in good agreement with those from recent (p, n) and (n, p) experiments. We show that a state-by-state comparison of (p, p′) and (e, e′) results has the potential of identifying pionic current contributions in (e, e′). The GT quenching factors in 54Fe are smaller than in the (s, d) shell probably because of severely truncated shell-model wave functions, particularly those of the nuclear ground state.

Charge-exchange contribution to the KrK-vacancy cross sections forCl15+,16+,17+-Kr collisions

1975 ◽  
Vol 12 (4) ◽  
pp. 1710-1712 ◽  
Author(s):  
Forrest Hopkins ◽  
Nelson Cue ◽  
Vince Dutkiewicz
Keyword(s):  
Charge Exchange ◽  
Cross Sections ◽  
Exchange Contribution

scholarly journals High-Energy Deuteron Cross Sections: Charge-Exchange Effects

1967 ◽  
Vol 156 (5) ◽  
pp. 1685-1697 ◽  
Author(s):  
R. J. Glauber ◽  
Victor Franco
Keyword(s):  
Charge Exchange ◽  
Cross Sections ◽  
High Energy ◽  
Exchange Effects

scholarly journals Four-body treatment of the K-shell positronium formation from multi-electron atoms

Open Physics ◽  
2014 ◽  
Vol 12 (3) ◽  
Author(s):  
Ebrahim Ghanbari-Adivi ◽  
Azime Velayati
Keyword(s):  
Cross Sections ◽  
Bound States ◽  
Transition Amplitude ◽  
Wave Functions ◽  
Positronium Formation ◽  
Distorted Wave ◽  
Helium Atoms ◽  
Three Body ◽  
Impact Energies ◽  
Correct Boundary Conditions

AbstractThe four-body Coulomb-Born distorted-wave approximation with correct boundary conditions (CBDW-4B) is applied to the K-shell positronium formation from multi-electron atoms at intermediate and high impact energies. In the present approach, both K-shell electrons are treated as active electrons. For collisions of positrons with helium, carbon, and neon atoms, both the post and prior forms of the transition amplitude are calculated and the corresponding differential and integral cross sections are compared with the results of the three-body version of the formalism (CBDW-3B). In order to investigate the effects of the static electronic correlations on the process, initial bound states of the active electrons in helium atoms are described by Hylleraas and Silverman wave functions. Also for positronium formation from helium atoms the obtained cross sections are compared with the available experimental data and also with the results of the other theories.

scholarly journals Production of Hypernuclei by Antiprotons

2018 ◽  
Vol 181 ◽  
pp. 01026
Author(s):  
Horst Lenske ◽  
Alexei Larionov
Keyword(s):  
Cross Sections ◽  
Production Cross ◽  
Beam Momentum ◽  
Wave Functions ◽  
Meson Exchange ◽  
Momentum Dependence ◽  
Final State ◽  
Final State Interactions ◽  
Pseudo Scalar ◽  
First Time

The production of hypernuclei is investigated for p̅+A→Λ‾+ΛA reactions in a covariant meson exchange approach. Besides the conventional pseudo-scalar (K) and vector (K*) channels, we study for the first time also contributions from the correlated πK scalar channel, described by the k/K*0 meson. Initial and final state interactions are considered by eikonal theory. The total and angular differential cross sections of the coherent process p̅+AZ→ΛA(Z−1)+Λ̅ are evaluated at the beam momenta 1:5…20 GeV/c within the meson exchange model with bound proton and Λ-hyperon wave functions. It is shown that the shape of the beam momentum dependence of the hypernucleus production cross sections with various discrete Λ states is strongly sensitive to the presence of the scalar k meson exchange in the p̅p→Λ̅Λ amplitude. This can be used as a clean test of the exchange by scalar πK correlation in coherent p̅A reactions.

Charge-Exchange Scattering of Pions on 14N

1971 ◽  
Vol 49 (13) ◽  
pp. 1826-1827 ◽  
Author(s):  
Arlene P. Maclin ◽  
J. M. Eisenberg
Keyword(s):  
Experimental Data ◽  
Shell Model ◽  
Charge Exchange ◽  
Cross Sections ◽  
Theoretical Calculations ◽  
Impulse Approximation ◽  
Wave Functions ◽  
Exchange Scattering ◽  
Low Amplitude ◽  
Model Formalism

Cross sections for the reaction 14N(π+,π0)14O are calculated near the (3, 3) resonance using the impulse approximation together with the Chew–Low amplitude in the framework of a two-hole shell model formalism. Various sets of wave functions are used and comparisons are made with existing experimental data and other theoretical calculations.

Total cross sections of the charge exchange reaction(π+,π0) on2H,3He, and4He across theΔ(1232)resonance

1999 ◽  
Vol 60 (2) ◽  
Author(s):  
A. Lehmann ◽  
D. Androić ◽  
G. Backenstoss ◽  
D. Bosnar ◽  
T. Dooling ◽  
...  
Keyword(s):  
Exchange Reaction ◽  
Charge Exchange ◽  
Cross Sections ◽  
Charge Exchange Reaction ◽  
Total Cross Sections
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