Study of ambiguities in π−p → ΛK0 scattering amplitudes
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Amplitudes for the reaction π − p → ΛK 0 are reconstructed from data on the differential cross section dσ/dΩ, the recoil polarization P, and on the spin rotation parameter β. At low energies, no data on β exist, resulting in ambiguities. An approximation using S and P waves leads only to a fair description of the data on dσ/dΩ and P; in this case, there are two sets of amplitudes. Including D waves, the data on dσ/dΩ and P are well reproduced by the fit but, now, there is a multitude of distinct solutions which describe the data with identical precision. In the range where the spin rotation parameter β was measured, a full and unambiguous reconstruction of the partial wave amplitudes is possible. The energy-independent (single-energy) amplitudes are compared to the energy-dependent amplitudes which resulted from a coupled-channel fit (BnGa2011-02) to a large data set including both pion- and photo-induced reactions. Significant deviations are observed. Consistency between energy-dependent and energy-independent solutions is obtained by choosing the energy-independent solution which is the closest to the energy-dependent solution. In a second step, the known energy-dependent solution for low (or high) partial waves is imposed and only the high (or low) partial waves are fitted leading to smaller uncertainties.
KeywordsPartial Wave Spin Rotation Partial Wave Amplitude Target Nucleon High Partial Wave
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