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.
open-access license: This is an open access article licensed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted, non-commercial use, distribution and reproduction in any medium, provided the work is properly cited.
* Address correspondence to this author at the CNRS/IN2P3, Institut de
Physique Nucléaire, UMR 8608, Univ. Paris-Sud, Orsay, 91405 Orsay,
France ; Tel: 33168156727; Fax: 33169156470; E-mail: email@example.com#Permanent address: CEA, IRFU, SPhN, Saclay, 91191 Gif-sur-Yvette Cedex,