Elastic backwardpd-scattering in ?-resonance region

Abstract

Contribution of A-resonance mechanism to elastic backward pd-scattering over T o = 0.5-0.8 GeV range of incident energy is analyzed. As distinct from [1-3], the parameters of NN~NA amplitudes in the phenomenology of one-meson 7c-and p-exchange are determined from pp~pn~ + reaction immediately in the kinematic region where the process pd~dp occurs. It has been found as a result that in the vicinity of the region where A-isobar is present on-mass-shell, the coherent sum of the amplitudes of A-resonance mechanism, relativistic one-nucleon exchange and single scattering predicts the pd ~ dp cross-section to be twice smaller than the experimental one and does not describe the tensor polarization of t2o deuteron. Possible causes of this discrepancy as well as the relation between the mechanisms of pd~dp process and the data on reactions of quasi-elastic knock-out of fast deuterons by protons (p, pd) from light nuclei, are discussed.

The reaction pd→(pp)n at high momentum transfer and short-range NN properties

“…This property of the ∆ mechanism was demonstrated earlier in Ref. [6] by comparing its contribution to the pd → dp cross section calculated with the RSC and Paris potentials, respectively. The increase of the ∆ contribution to the breakup cross section by approximately 50% for the CD Bonn potential fills in much of the ONE dip [8,9,11] of the cross section (cf.…”

New mechanism for intermediate- and short-range nucleon-nucleon interaction

“…Even if one forgets for the moment the nuclear pion dynamics, the large value of Λ πN N ≃ 1.3 ÷ 2.0 GeV seems to be fully incompatible with the description of pion production in collisions pp → pnπ + [25] and also with elastic backward p + d scattering [18,19]. Let us to add to this collection still an another example: a small value of Λ πN N = 0.528 GeV has been found by T. Cohen [26] in his analysis for πNN form factor within the Skyrme model.…”

“…As a result, the shell-model matrix elements of the vertex operator (12) will only contribute to the transition amplitudes of Eqs. (20) and (18).…”

“…Hence in OBE models using such a heavy-meson mechanism it is first necessary to justify the employment of "free-space" meson-nucleon coupling constants and cut-off form factors. As a result of this, all existing OBE models have severe problems with the short-range cut-off parameters Λ [6,7,9,[17][18][19] (see especially the severe critique in [17] and also in the next Subsection). Thus all the short-range parts of OBE potentials are treated purely phenomenologically [5][6][7][8] but using at the same time the Yukawa framework which looks rather inadequate for such short ranges.…”

“…It is well known [5,6,17] that in all the OBE models the values of the cut-off parameter Λ mN N (m = π, σ, ρ, ω...) are strongly increased as compared with any microscopic model for meson-baryon coupling and also as compared with fits to the data of meson-nucleon scattering experiments [20,21,18,19]. This disagreement is especially evident in the values of Λ πN N which can be derived from the theory of πNN form factors [17,20,22] and even from direct experiments N(e, e ′ π)N ′ in which a pion is knocked out from the pion cloud of the nucleon by fast electrons [23].…”