Pion-He scattering length |
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Authors: | J. De Kam W. Verkley H. Van Doremalen |
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Affiliation: | Natuurkundig Laboratorium der Vrije Universiteit, Amsterdam, The Netherlands |
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Abstract: | We present relativistic three-body calculations for the real part of the π-4He scattering length Re a. Nucleon binding, exclusion principle and Fermi motion are all included in a very careful manner. Because of our careful evaluation of the single-scattering process the remaining discrepancies with the experimental data can be attributed to higher-order mechanisms involving more than one nucleon. In particular for the πA S-wave interaction at threshold, one expects that these higher-order contributions arise largely from the absorption effect. We have performed our calculations for four current models of the input πN t-matrix. Using a πN t-matrix which reproduces the low energy πN phase shifts correctly leads to Re aabs -Im aabs, if we attribute the discrepancy of the calculated value with the accurately determined empirical value of Re a to pion absorption. We determine the strength parameter B0 in a p2 optical potential term from an adjustment to the π-4He scattering length. Finally some cross sections are calculated for Tlabπ = 10 MeV and Tlabπ = 15 MeV. |
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