Manifestation of theP-wave diproton resonance in single-pion production inppcollisions

Abstract

It is demonstrated that many important features of single-pion production in pp collisions at intermediate energies (T p ≃ 400-800 MeV) can naturally be explained by supposing excitation of intermediate diproton resonances in pp channels 1 D 2 , 3 F 3 and 3 P 2 , in addition to conventional mechanisms involving an intermediate ∆-isobar. We predict for the first time the crucial role of the 3 P 2 diproton resonance, found in recent experiments on the single-pion production reaction pp → pp( 1 S 0 )π 0 , in reproducing the proper behavior of spin-correlation parameters in the reaction pp → dπ + which were poorly described by conventional meson-exchange models to date. The possible quark structure of the P -wave diproton resonances is also discussed.

To the Nature of Nuclear Force

“…The main argument however is that in the ground of the dibaryon concept there is an experimentally verified assumption about the dominating role of dibaryon resonances in NN interaction in each partial-wave channel. Besides, the present authors have shown in a series of papers [42][43][44] that the observed dibaryon characteristics are in good agreement with the experimental cross sections for one-and two-pion production in NN collisions at intermediate energies T N ∼ 1 GeV.…”

“…It is important to note here that a similar conclusion about the dominance of the dibaryon mechanism in inelastic NN interaction in the 3 P 2 channel was made by us when analyzing the single-pion production reaction pp → dπ + at energies from the threshold to about 800 MeV [44].…”

“…9 It is important to emphasize that the parameters of the 3 P 2 dibaryon that were found in Ref. [44] turned out to be also very close to the experimental ones [22]. Thus, the results of the present work not only confirm the conclusion that the 3 P 2 dibaryon dominates the inelastic NN interaction up to energies of T lab ≃ 600 MeV, but, even more importantly, they allow us to make the conclusion about the decisive role of this resonance also in elastic NN scattering in the same energy region.…”

On the history of dibaryons and their final observation

“…Only by inclusion of the formation and the decay of dibaryon resonances -in particular the D 12 resonance with I(J P ) = 1(2 + ) in the 1 D 2 N N partial wave -in the intermediate reaction process a proper description of the experimental data can be obtained. By additional inclusion of corresponding resonances in 3 F 3 and 3 P 2 partial waves even polarization observables can be quantitatively described for the first time [207].…”

Nature of $\bm{S}$-wave $\bm{NN}$ interaction and dibaryon production at nucleonic resonance thresholds

“…There is suggestive evidence for the existence of still further states like a P -wave I(J P ) = 1(3 − ) state, for which, however, the experimental situation is not yet as clear [16]. It is also worth emphasising that the three resonances 1(2 + ), 1(2 − ) and 1(3 − ) have been shown to give a sizeable contribution to the pp → dπ + cross sections and polarisation observables [31] (the resonance 1(0 − ) is not allowed in this reaction by the parity and momentum conservation).…”