Abstract
We derive, in model-independent way, the spin structure of the matrix element for the reaction of associative Θ+-pentaquark production, π ± + d → Θ+ + Σ±, in the threshold region and in collinear kinematics. The expressions for the polarization observables in this reaction are found assuming spin 1/2 and different parities for Θ+. We have proved that such a reaction can be used for a model-independent determination of the P parity of Θ+ only by measuring the Θ+ polarization. Other polarization observables, such as the dependence of the Σ± polarization on the vector and tensor deuteron polarizations, are insensitive to the Θ+ parity under the considered kinematical conditions. The linear and quadratic relations between polarization observables in \(\pi ^ \pm + \vec d \to \Theta ^ + + \vec \sum ^ \pm \) (Θ+ is unpolarized) do not depend on the parity of the Θ+ pentaquark. The analysis performed for this reaction is also applicable without any modification to the reaction K + + d → Θ+ + p. Using the pole model for the reaction mechanism, we estimated the value of the cross section for the reaction K + + d → Θ+ + p near the threshold.
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Gakh, G.I., Rekalo, A.P. & Tomasi-Gustafsson, E. Θ+-Pentaquark parity from associative baryon production in πd collisions, π ± + d → Θ+ + Σ± . Phys. Atom. Nuclei 69, 909–914 (2006). https://doi.org/10.1134/S1063778806050140
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DOI: https://doi.org/10.1134/S1063778806050140