Theta(+)-pentaquark parity from associative Baryon production in pi d collisions, pi(+/-)+d ->Theta(+)+Sigma(+/-)

摘要

We derive, in model-independent way, the spin structure of the matrix element for the reaction of associative Theta(+)-pentaquark production, pi(+/-) + d --> Theta(+) + Sigma(+/-), 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 Theta(+). We have proved that such a reaction can be used for a model-independent determination of the P parity of Theta(+) only by measuring the Theta(+) polarization. Other polarization observables, such as the dependence of the Sigma(+/-) polarization on the vector and tensor deuteron polarizations, are insensitive to the Theta(+) parity under the considered kinematical conditions. The linear and quadratic relations between polarization observables in pi(+/-) +(d) over right arrow --> Theta(+) + (Sigma) over right arrow (+/-) (Theta(+) is unpolarized) do not depend on the parity of the Theta(+) pentaquark. The analysis performed for this reaction is also applicable without any modi. cation to the reaction K+ + d --> Theta(+) + p. Using the pole model for the reaction mechanism, we estimated the value of the cross section for the reaction K+ + d --> Theta(+) + p near the threshold.