Search for narrow nucleon resonances below pion threshold in theH(e,e′π+)X

Abstract

In two series of high-resolution coincidence experiments at the three-spectrometer facility at MAMI, the H(e,eЈ ϩ )X and 2 H(e,eЈp)X reactions were studied to search for narrow nucleon resonances below pion threshold. The missing-mass resolution was 0.6-1.6 MeV/c 2 full width at half maximum in the proton experiment and 0.9-1.3 MeV/c 2 in the deuteron experiment. The experiments covered the missing-mass region from the neutron mass up to about 1050 and 1100 MeV/c 2 , respectively. None of our measurements showed a signal for narrow resonances to a level of down to 10 Ϫ4 with respect to the neutron peak in the missing-mass spectra.

Supernarrow Dibaryons

“…However, in experiments on a single nucleon, no any significant structure was observed [26][27][28]. Therefore, the question about a nature of the peaks observed in [13,20] remains open at present.…”