Peripheral Production of Resonances

We review the peripheral cross‐sections of resonances that cannot be produced by π‐exchange. Explicitly we consider the four nonets of mesons n the $\mathrm{L}\text{\hspace{0.17em}=\hspace{0.17em}1}$ quark classification, ${\mathrm{J}}^{\mathrm{P}}{\text{\hspace{0.17em}=\hspace{0.17em}0}}^{+}$ π_N(980); 1⁺, e.g., A₁, B; 2⁺, e.g., A₂. We detail the constraints of SU₃, exchange degeneracy, factorization, pole extrapolation, Watson's theorem and duality as they have been gleaned from long and painful study of well‐loved reactions. The controversial nature of the 0⁺ and 1⁺ nonets is related to a surprising suppression of their cross‐sections (which are around 10 μb at 5 GeV/c) in non‐diffractive processes. This is explained by a generalized vector meson photon analogy model recently proposed by Kislinger. We predict all differential cross‐sections for these $\mathrm{L}\text{\hspace{0.17em}=\hspace{0.17em}1}$ quark states and show that these mesons are best studied in hypercharge exchange reactions, e.g., ${\pi }^{-}\mathrm{p}{\mathrm{\hspace{0.17em}\Rightarrow \hspace{0.17em}Q}}^0\Lambda$ and ${\mathrm{K}}^{-}\mathrm{n}{\mathrm{\hspace{0.17em}\Rightarrow \hspace{0.17em}A}}_1^{-}\Lambda$ . An explanation, using final state interaction theory, of the large background under the Q and A₁ observed in diffractive processes, suggests that quantum numbers of mesons are best studied in non‐diffractive reactions of the type mentioned above.