Measurement of the complete spin density matrix of the Y∗ (1385) in 8 GeV/c π+p and 10 GeV/c K−p interactions and comparison with quark model predictions

Parity conserving decays yield incomplete information about the spin state of a decaying resonance. Using the cascade decay Y∗ (1385) → Λπ (Λ → pπ), where the second decay does not comserve parity, one finds all the parameters necessary to specify the spin state of Y∗ resonances. In this paper Y∗ resonances produced in π+p reactions at 8 GeV/c and K−p reactions at 10 GeV/c are studied. It is found that the experimental results are, with one exception, in resonable agreement with the predictions of the additive quark model.