arXiv subjects

Karlheinz Langanke

Publications and source records attributed to Karlheinz Langanke.

22 records · Page 2Linked to original sources

arXiv1998

Large-space cluster model calculations for the He3(He3,2p)He4 and H3(H3,2n)He4 reactions

The He3(He3,2p)He4 and H3(H3,2n)He4 reactions are studied in a microscopic cluster model. We search for resonances in the He3+He3 and He4+p+p channels using methods that treat the two- and three-body resonance asymptotics correctly. Our results show that the existence of a low-energy resonance or virtual state, which could influence the Be-7 and B-8 solar neutrino fluxes, is rather unlikely. Our calculated He3(He3,2p)He4 and H3(H3,2n)He4 cross sections are in a good general agreement with the experimental data.

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arXiv1998

Effects of B-8 size on the low-energy Be7(p,gamma)B8 cross section

We calculate several "size-like" B-8 observables within the microscopic three-cluster model and study their potential constraints on the zero-energy astrophysical S_{17}(0) factor of the Be7(p,gamma)B8 reaction. We find within our three-cluster model that a simultaneous reproduction of the experimental data for the B-8 radius and quadrupole moment and of the B8-Li8 Coulomb displacement energy implies S_{17}(0)=(23-25) eVb.

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arXiv1998

Isovector Pairing in Odd-A Proton-Rich Nuclei

A simple model based on the group SO(5) suggests that both the like-particle and neutron-proton components of isovector pairing correlations in odd-A nuclei are Pauli blocked. The same effect emerges from Monte Carlo Shell-model calculations of proton-rich nuclei in the full fp shell. There are small differences between the two models in their representation of the effects of an odd nucleon on the competition between like-particle and neutron-proton pairing, but they can be understood and reduced by using a two-level version of the SO(5) model. On the other hand, in odd-odd nuclei with N not equal to Z SO(5) disagrees more severely with the shell model because it incorrectly predicts ground-state isospins. The shell model calculations for any fp-shell nuclei can be extended to finite temperature, where they show a decrease in blocking.

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arXiv1995

Parity-violating alpha-decay of the 3.56-MeV J,T=0+,1 state of Li-6

We study the parity-violating alpha+d decay of the lowest 0+ state of Li-6 in a microscopic three-cluster model. The initial bound and the final scattering states are described consistently within the same model. The parity-violating decay width is calculated in perturbation theory using the parity-nonconserving nucleon-nucleon interaction of Desplanques, Donoghue, and Holstein (DDH). We find that the decay width is sensitive to dynamical degrees of freedom which are beyond the alpha+p+n model, for example, alpha excitation and breakup. In our full model, which contains breathing excitations of the alpha particle and H-3 + He-3 rearrangement, the parity-nonconserving decay width is Gamma=3.97x10^{-9} eV, using the DDH coupling constants.

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