Hidden dibaryons in one- and two-pion production in NN collisions

Abstract

Processes of one-and two-pion production in NN collisions are considered in connection with excitation of intermediate dibaryon resonances. In particular, relative contributions of the conventional meson-exchange and dibaryon excitation mechanisms in the reaction pp → dπ + are investigated in detail. Inclusion of the intermediate isovector dibaryon resonances is shown to essentially improve the description of experimental data for this reaction, provided the soft meson-baryon form factors consistent with πN elastic scattering are used. Manifestation of the intermediate isoscalar and isovector dibaryons in the two-pion production processes is also studied. The role of the isovector dibaryon resonances in the reaction pp → ppππ is discussed for the first time. An explanation of the observed strong differences between two-pion production cross sections in pn and pp collisions based in part on the analysis of dibaryon structure is suggested.

The d ⁎ (2380) dibaryon resonance width and decay branching ratios

“…This peaking, essentially at the D 12 (2150) mass value, suggests that the πD 12 two-body channel plays an important role in the decay modes of the d * (2380) dibaryon, as reflected in the calculation of Ref. [20] depicted in the figure. The width of this invariant-mass distribution, nevertheless, agrees roughly with Γ d * (2380)=80±10 MeV irrespective of the underlying decay mechanism.…”

Examination of the nature of the ABC effect

“…Recently Platonova and Kukulin proposed an alternative explanation of the ABC effect [59,60]. They consider two possible decay branches for the d * (2380) resonance.…”

“…However, in Ref. [60] it is argued qualitatively that due to the much increased phase space for the unbound N N system the centrifugal barrier for the d-wave emission of the σ meson plays here a much bigger role and might suppress its emission more than in the dππ case. Unfortunately, a convincing quantitative calculation has not yet been presented by these authors.…”

Non-strange dibaryons studied in the γd → π0π0d reaction

“…They obtain M =2.38 (2.15) GeV/c 2 for D 03 (D 12 ) by solving πN ∆ (πN N ) Faddeev equations. Platonova and Kukulin predicts the D 03 → πD 12 decay, and additional isoscalar and isovector dibaryons [14]. Experimentally, D 12 is given as the 3 P 2 multipole strength at M =2.18 GeV/c 2 in π ± d elastic scattering by a partialwave analysis [15].…”