Global description of0−12+→0−12+reactions utilizing the bare Pomeron

Abstract

It is shown that the combination of a "bare Pomeron" with intercept ${\hat{\alpha }}_P\mathrm{}\left(0\right)=0.85\mathrm{}$ in conjunction with a reasonable set of secondary Regge trajectories and a canonical absorption prescription is capable of providing a good global fit to practically all $0^{-}{\frac{1}{2}}^{+}\to 0^{-}{\frac{1}{2}}^{+}$ meson-nucleon scattering data up to lab momenta of 30 GeV/c. The bare Pomeron with intercept lower than 1 has a large real part which greatly facilitates the description of the data. At higher energies, "renormalization" effects can be expected to be important as inelastic diffraction events, and these lead to a renormalized Pomeron intercept very close to or equal to one. The value ${\hat{\alpha }}_P\mathrm{}\left(0\right)=0.85\mathrm{}$ used throughout this intermediate-energy fit is in agreement with current inclusive triple-Regge data and maximum-rapidity-gap distributions. It is also in agreement with certain strong-coupling ABFST (Amati-Bertocchi-Fubini-Stanghellini-Tonin) multiperipheral model calculations. For secondary effects, we have used a family of vector Regge trajectories ($\rho ,\omega ,K^{*}$) with a degenerate intercept of about 0.45, and tensor trajectories ($A_2,K^{**}$) with an intercept of about 0.25. A second vacuum pole emerges with intercept close to 0. The $p^{\prime } \mathrm{}\left(f\right)\mathrm{}$ trajectory, not included here, can perhaps be expected to appear in conjunction with the renormalization of the Pomeron. Although no wrong-signature nonsense zeros are included in the parametrization, the $\rho -A_2$ and $K^{*}-K^{**}$ pole couplings are nevertheless very nearly exchange degenerate. SU(3) is used to relate most of the other couplings. The (pole + cut) helicity-flip $\rho -A_2$ and $K^{*}-K^{**}$ amplitudes also show considerable exchange-degenerate characteristics. We have used a standard absorption prescription to calculate the second-order bare Pomeron $\left(\hat{P}\right)\otimes$ Reggeon cuts and $\hat{P}\otimes \hat{P}$ cuts. An unusual result emerges—the "enhancement" ${\lambda }_i$ factors for all cuts are less than one. This indicates the presence of higher-order cuts which thus dominate over inelastic intermediate-state production in this approach. The data used in this fit are a representative selection of $0^{-}{\frac{1}{2}}^{+}\to 0^{-}{\frac{1}{2}}^{+}$ data (including $\pi N$ amplitude analysis, hypercharge-exchange differential cross sections and polarizations; ${\pi }^{\pm }p$ and $K^{\pm }p$ total and differential cross sections, polarizations, and $t=0\mathrm{}$ real-to-imaginary ratios; and $\pi N$ and $\mathrm{KN}$ charge-exchange differential cross sections and polarizations) up to $p_{\mathrm{lab}}=30\mathrm{}$ GeV/c and $\mathrm{}\left|t\right|=1.5\mathrm{}$ ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^2$.