Some Comments on the Putative ${\Theta }^{+}$ (1543) Exotic State

Abstract

We point out that existing $K^{+}d$ scattering data available in the PDG (Particle Data Group compilation) suggest some fluctuations in those momentum bins where the (Fermi motion broadened) ${\Theta }^{+}$[1543] resonance recently indicated in many gamma nuclear reactions and predicted six years ago by Diakonv Petrov and Polyakov might have shown up. The I=0, $J^P={1/2}^{+}$ P-wave channel should have a universal peak cross section of $\sim 37$ mb at resonance. The smallness of the effect seen in $K^{+}d$ with the $\delta \sigma$ fluctuations being less than 4 mb imply an indirect bound ${\Gamma }_{{\Theta }^{+}}<6$ MeV, far stronger than the direct gamma-d measurements. This renders the theoretical interpretation of the new state very difficult.

10 pages, no figures, RevTex 4