科研之友
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<正>Since several decades, a particular attention has been devoted to hadrons with anomalous properties [1–5]. On the experimental side, the search has been very difficult and disappointing. For instance, in the early 60’s, there has been some claims for baryon resonances with strangeness S=+1, the so-called Z baryons, while the established baryons have either S=0 or S < 0. But the Z spectrum was based on somewhat hazardous analyses of K+-nucleon scattering data without spin observables, and it faded away. It reappeared under the name of θ pentaquark, but it was never firmly established.
