CNRS/IN2P3, Institut de Physique Nucléaire, UMR 8608, Univ. Paris-Sud, Orsay, 91405 Orsay, France
Existing data exhibit signatures of small peaks, often not commented by the authors. These peaks are tentatively associated to narrow exotic low mass unflavored mesons. Increasing confidence for the existence of such mesons is obtained from various measurements performed for different aims. These data are discussed and their masses are compared with previously observed low mass mesonic structures. Attempts are presented to interpret the data and classify them according to a simple scheme.
Keywords:: Narrow low mass, not
q¯q mesonic structures, tentative association to tetra-quark clusters.
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