Multiperipheral and diffractive components of the total cross section in Gribov's Reggeon calculus

Abstract

The usual classification of multiparticle processes into those with no large rapidity gaps (multiperipheral) and those with at least one large gap (diffractive) is made in the framework of Gribov's Reggeon calculus. (A rapidity gap is defined to be large if it exceeds a fixed, critical gap size ${\ensuremath{\xi}}_{c}$.) General formulas for the multiperipheral and diffractive contributions to the total cross section are obtained by cutting the leading Reggeon diagrams in the elastic amplitude and analyzing the intermediate states. The cutting procedure is always applied to physical Pomeranchukons. In obtaining our results, we assume that when a physical Pomeranchukon with rapidity span $\ensuremath{\xi}$ is cut, the probability $p(\ensuremath{\xi})$ of having a multiparticle intermediate state with no large rapidity gaps is given by $p(\ensuremath{\xi})={e}^{\ensuremath{-}\ensuremath{\gamma}\ensuremath{\xi}}$, $\ensuremath{\gamma}>0$. This form is shown to be reasonable if long-range correlation effects are not important. Our results depend on the new parameter $\ensuremath{\gamma}$, which is of course a function of the critical gap size ${\ensuremath{\xi}}_{c}$. At CERN ISR energies, the Pomeranchukon-cut contributions are found to be very important, and must be included along with the pole contribution.