Observation of an Anomalous Structure in Proton Polarization from Deuteron Photodisintegration

Short range behaviour of the N-N potential within the quark Model

“…This is one of the channels where dibaryon resonances have been suggested. Our result supports the existence of the di-baryon resonance proposed by Kamae and Fujita [6]. However, in such a case where the potential around the origin is attractive, the expansion method is not valid, and we have to rigorously solve the nonlocal RGM equation.…”

“…On the other hand, the (S, T)=(3,3), (3,2) and (2,3) channels in the AA case have to have a Pauli 'hard core'. The most interesting result is that in the (S, T)=(3, 0) channel we expect an attractive potential at short distances, which would support the proposed baryon resonance in the A A system [6]. Our microscopic approach, however, has a few shortcomings that may hinder more quantitative calculations.…”

“…3, the relevant quantities are calculated for the NN system. We consider also the AA case, whose short range behaviour may have some relevance for the di-baryon resonances [6]*. In Sect.…”

On the history of dibaryons and their final observation

“…Actually groups at Tokyo had been quite close already as early as 1977 considering measurements of the proton polarization in deuteron photodisintegration γd → pn [129,130,131,132]. They observed a strong increase of the polarization at energies beyond √ s = 2.2 GeV, reaching a maximum around 2.38 GeV and decreasing thereafter.…”

“…In the seventies measurements of this particular reaction were extended up to 700 MeV photon energy using Bremsstrahlung photons produced by electrons accelerated in the synchrotron at Tokyo. As a result it was observed that the polarization at 90 • starts rising at 300 MeV, reaches a maximum around 500 MeV and starts dropping above 550 MeV describing thus a resonance-like excitation function [129]. It was suggested that this behavior could be due to the excitation of a dibaryon resonance with a mass of 2380 MeV and preferably with quantum numbers I(J P ) = 0(3 + ) as predicted in 1964 by Dyson and Xuong [33] and -in close connection with the Bremsstrahlung measurements -by Kamae and Fujita [99] based on a non-relativistic one-boson exchange potential model.…”