Search for Low Mass Exotic mesonic structures. Part II attempts to understand the experimen.pdfVIP

Search for Low Mass Exotic mesonic structures. Part II: attempts to understand the experimental results B. Tatischeff1,2 1CNRS/IN2P3, Institut de Physique Nucl´eaire, UMR 8608, Orsay, F-91405 2Univ. Paris-Sud, Orsay, F-91405, France E. Tomasi-Gustafsson3 3DAPNIA/SPhN, CEA/Saclay 7 0 91191 Gif-sur-Yvette Cedex, France 0 2 Our previous paper, part I of the same study, shows the different experimental spectra used to conclude on the genuine existence of narrow, weakly excited mesonic structures, having masses below t c and a little above the pion (M=139.56 MeV) mass. This work [1] was instigated by the observation, O in the Σ+ disintegration: Σ+ →pP0 , P0 → µ−µ+ [2], of a narrow range of dimuon masses. The authors conclude on the existence of a neutral intermediate state P0 , with a mass M=214.3 MeV 9 ± 0.5 MeV. We present here some attempts to understand the possible nature of the structures observed in part I. ] x PACS numbers: 13.60.Le, 14.40.Cs, 14.80.-j e - l c I. INTRODUCTION u n [ In part I of the same study [1], several spectra were 1 presented, showing narrow and weakly excited struc- v tures, having masses below and just above the pion mass 8 (M=139.56 MeV). These data are mainly missing mass 9