Tübingen 2003 – wissenschaftliches Programm
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HK: Physik der Hadronen und Kerne
HK 13: Poster-Sitzung: Theorie
HK 13.13: Poster
Dienstag, 18. März 2003, 13:30–15:30, Foyer
Isovector nuclear spin-orbit interaction from chiral pion-nucleon dynamics — •Norbert Kaiser — Physik Department T39, Technische Universität München, D-85747 Garching
Using the two-loop approximation of chiral perturbation theory, we calculate the momentum and density dependent isovector nuclear spin-orbit strength Vls(p,kf). This quantity is derived from the spin-dependent part of the interaction energy Σspin = i/2 σ→· (q→ ×p→ )[Uls(p,kf)− Vls(p,kf)τ3 δ] of a nucleon scattering off weakly inhomogeneous isospin-asymmetric nuclear matter. We find that iterated 1π-exchange generates at saturation density, kf0=272.7 MeV, an isovector nuclear spin-orbit strength at p=0 of Vls(0,kf0) ≃ 50 MeVfm2. This value is about 1.4 times the analogous isoscalar nuclear spin-orbit strength Uls(0,kf0)≃ 35 MeVfm2 generated by the same two-pion exchange diagrams. We also calculate several relativistic 1/M-corrections to the isoscalar nuclear spin-orbit strength. In particular, we evaluate the contributions from irreducible two-pion exchange to Uls(p,kf). The effects of the three-body diagrams constructed from the Weinberg-Tomozawa ππ NN-contact vertex on the isoscalar nuclear spin-orbit strength are computed. We find that such relativistic 1/M-corrections are less than 20% of the isoscalar nuclear spin-orbit strength generated by iterated one-pion-exchange, in accordance with the expectation from chiral power counting. Work supported in part by BMBF, DFG and GSI.