New evidence for supernarrow dibaryons production in pd interactions

Abstract

The reaction pd → pX at 305 MeV is studied with the aim to search for supernarrow dibaryons, the decay of which into two nucleons is forbidden by the Pauli exclusion principle. The experiment was carried out at the Moscow Meson Factory using the spectrometer TAMS, which detected the scattered proton and another charged particle (either p or d) from the decay of X. Narrow peaks in missing mass spectra have been observed at 1905 and 1924 MeV. Comparison of the obtained data with theoretical predictions leads to the conclusion that the peak found at 1905 MeV most likely corresponds to a supernarrow dibaryon with the isotopic spin equal to 1. The possible origin of the peak at 1924 MeV is also discussed.

Supernarrow Dibaryons

“…The mass values found are very close to the values obtained in INR [12,13] The peak at M = 1926 MeV in the bottom panel corresponds to the expected value. However, this peak is too wide, possibly due to insufficient accuracy in the determination of experimental data in the region of this resonance.…”

“…In the experimental missing mass M X1 spectrum besides the peak at the neutron mass due to the process pd → p+pn, a resonance-like behavior of the spectrum has been observed at 966 ± 2, 986 ± 2, and 1003 ± 2 MeV [13,[17][18][19]. These values of M X1 coincide with the ones obtained by the simulation and essentially differ from the value of the neutron mass (939.6 MeV).…”

“…The linear polarization of initial photon was approximately 99%. The results of this experiment and their comparison with the data obtained at INR [12,13] are shown in Fig. 7.…”

“…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.…”

“…However, in contrast to the ref. [12][13][14][15][16][17][18][19], the authors of these works did not study either the correlation between the parameters of the scattered proton and the second detected particle or the emission of the photon from the dibaryon decay. Therefore, in these works the relative contributions of the dibaryons under consideration were small, which hampered their observation.…”