The scattering of two pseudoscalar mesons belonging to the octet representation of S${\mathrm{U}}_3$ is studied in the framework of bootstrap dynamics. It is found that the leading Regge poles correspond to a singlet and two octet S${\mathrm{U}}_3$ representations. The singlet state is unambiguously identified with the Pomeranchuk trajectory, and one of the octets corresponds to the well-known vector mesons. The other octet is composed of even-signature poles which are called $P^{\prime }$, $Q$, and $R$, and which, in a first approximation, coincide in position with the vector-meson trajectories. These poles are not likely to manifest themselves as low-mass particles or resonances because of their positive signature, but they are expected to influence appreciably high-energy scattering in the crossed channel. In particular, the $P^{\prime }$ pole plays the role of the second vacuum trajectory proposed by Igi, and the $R$ is suitable to explain, through an interference with the $\rho$ pole, the sign, value, and high-energy dependence of the difference between total $\mathrm{pp}$ and $\mathrm{np}$ cross sections.

• Received 12 December 1963

DOI:https://doi.org/10.1103/PhysRev.134.B630