Partial Wave Amplitude for Low Mass N System Produced in Diffraction Dissociation

Abstract

Partial wave amplitudes of the Drell-Hiida-Deck model and its unitarized version by the final state interaction are studied for the low mass Nn system produced in the diffraction dissociation process. The partial wave amplitude unitarized by the final state interaction can be divided into two components. The one has the minimum and the other the maximum at the resonance position. The resultant amplitudes violate the Gribov-Morrison rule and the conservation of the t-channel helicity. with small transferred four momen­ tum squared, t, at PL=5GeV/c to PL=40GeV/c have revealed the internal structures of a low mass diffraction dissociation (LMDD). These analyses seem to show that the A 1 enhancement cannot be a typical resonance with the Breit­ Wigner phase. If there are no axial vector mesons at all, our theoretical framework such as composite models or higher symmetries would encounter serious difficulties. It is, therefore, a highly important problem to clarify whether the A 1 enhancement in LMDD is really kinematical or not. For this purpose it is very useful to analyse an Nn system produced diffractively by a process nN--'>n(1\fn) for an example, because we can compare directly the structure of the Nn system with that in the nN phase shift analyses. Preliminary partial wave analyses on the diffractively produced Nn system have recently been started. oJ~n According to their analyses and other data on the Nn LMDDsJ. g) it is indicated that the Nn mass distribution at the smallest It I region has a peak at MN <1.35 Ge V which is much lower than that expected from the masses of the resonances. We have already encountered similar phenomena in the pion photoproduction processes at the resonance region10 J or in the p photo­ production process.ll) These phenomena are considered to be due to an interference effect between a resonance production term and some kind of background term. In this paper we study the partial wave analyses of the Drell-Hiida-Deck (DHD) modeP2J and of the unitarized version of the DHD model by the final state interaction. We do not use the Reggeized DHD amplitude, because we are interest­ ed in LMDD up to the third resonance region at most and its partial wave analysis. (The reason why we do not use the Reggeized DHD and the interpolation of the elementary pion-exchange amplitude to the Reggeized one will be discussed in