Breaking of Line Reverse Relation and Exotics

Abstract

Under a hypothesis that the meson-baryon reaction amplitude corresponds to the urbaryon rearrangement diagram (URD), the X type (t-u dual) URD is related to the H type (s-t dual) one in the forward region by reversing the urbaryon line. It has been taken that the X type amplitude has the magnitude equal to the H type one and is real, and that the Z .type (s-u dual) amplitude is negligible; line reverse relation (LRR). There are, however, indications that the LRR is more or less broken. Two simple models resulting in the LR breaking under the URD hypothesis are investigated. (1) Zrr model. One· of the three Z type URD's, which is named Zrr, has a remarkable peculiarity that its t-channel quantum numbers are non-exotic irrespective of the exoticfour­ urbaryon configuration. If the Zrr amplitude survives up to high energies from this peculiarity, an apparent LR breaking results in KN-'nrY vs. rrN~KY processes. (2) Im X model. The imaginary part of the X amplitude, which may be compatible with the possible KN s-channel exotics such as Zo (P112) and Z 1 (P,;,), gives rise to an intrinsic LR breaking. A comparison between the two models and their consequences are examined. LR breakings in decuplet baryon production and of baryon exchange are also discussed.