Se p 19 98 Hadronization mechanisms and longitudinal polarization of Λ in e + e − annihilation at high energies ∗

We suggested that longitudinal polarization of Lambda produced in e + e − annihilation at LEP energies can provide useful information on hadronization mechanism in general and on testing the validity of different pictures for the spin content of baryon in describing the fragmentation process in particular. We present the results obtained from the calculations based on two very much different pictures. We compare the results with the recent ALEPH data and make suggestions for future measurements. 0 In this talk, I would like to discuss a question which we met in our study on spin effects in hadron production processes and the efforts we made toward solving this problem. The work which I will present in the following has been done in collaboration with Dr. Boros. The main ideas and results have already been published in [1]. As you certainly know, there exist now in literature two completely different pictures for the spin contents of the baryons: According to the static (or constituent) quark model, spin of a baryon belonging to the J P = 1 2 + octet is completely determined by the three valence quarks. The sum of the spins of these valence quarks is the spin of the baryon. This picture is very successful in describing the static properties of the baryons. But according to the the data from polarized deep inelastic lepton-nucleon scattering [2] and SU(3) flavor symmetry in hyperon decay, the sum of the spins of the three valence quarks is only a small fraction of the spin of the nucleon. A large part of the baryon spin originates from the orbital angular momenta of the valence quarks and/or from the sea (i.e. the sea quarks, antiquarks and gluons). Hence, we met a question: Which picture is suitable in describing the spin effects in the fragmentation process? Obviously, the answer to this question can be different in different hadronization models. Hence, study of this question should be able to provide also further test of these models. Usually, we say that, in the hadronization process, a quark and an antiquark combine to form a meson or three quarks combine together to form a baryon. In this way, we consider only the valence quarks of the hadron but neglect the sea. It seems that here the SU(6) wave function based on the static quark model should be suitable. Surely, whether this is indeed true is a …