Charge exchange reactions on proton and exotic low-mass baryons
Résumé
This contribution aims to give further evidence for the existence of low mass exotic baryons. Narrow structures in baryonic missing mass or baryonic invariant mass were previously observed. Since their existence is sometimes object of controversy, different data, measured with incident hadrons, by different collaborations, are reanalyzed to add informations on the possible existence of these narrow exotic baryonic resonances. These strucures are clearly exotic as there is no room for them in the qqq configurations, since their width is smaller than the widths of ”classical” PDG baryonic resonances, and also since some masses lie below the pion threshold mass. Previous experiments, performed at SPES3 and SPES4 (Saturne) thanks to good resolution and high statistics, exhibit clearly narrow structures in different hadronic masses. The observation in different conditions (reaction, incident energy, spectrometer angle, or observable) at the same mass (within ±3 MeV) was considered a confirmation of their existence [1]. Additional data are shown, namely the cross-sections of the following reactions: pp!n++, p(d,2p)0, 12C(d,2p)X, p(3He,t)++, d(3He,t)X, p(12C,12N)X, and p(20Ne,20F)++. An example is illustrated in Fig. 1 where the cross section of the p(12C,12N)0 reaction at T p=1100 MeV/N, =00 [2] is shown. A clear oscillatory shape is observed, well fitted with the masses of the previously extracted narrow structures indicated by greek letters.