Average charged-particle multiplicities inπ−pinclusive reactions at 147 GeV/c

Abstract

The experimentally determined average charged-particle multiplicities, $〈n_X〉$, of the systems, $X$, produced in the following reactions for 147 GeV/c incident pion momentum are presented as functions of the square of the invariant mass of $X$, ${M_X}^2$, and of $\mathrm{}\left|t\right|:{\pi }^{-}p\to {\pi }_{\mathrm{fast}}^{-}X$, ${\pi }^{-}p\to \mathrm{pX}$, ${\pi }^{-}p\to {\Delta }^{++}X$, ${\pi }^{-}p\to {\left({\pi }^{-}{\pi }^{+}\right)}_{{\rho }^0}X$, and ${\pi }^{-}p\to {\Lambda }^{0}X$. Details of the analysis are discussed. These data can be fit by the expression $〈n_X〉=A+B \ln {M_X}^2+C\left|t\right|\mathrm{}$ and the coefficients obtained for $B$ are equal within their uncertainties. $C$ is significantly different from zero only for ${\pi }^{-}p\to {\pi }_{\mathrm{fast}}^{-}X$. These results and $〈n_X〉$ data from other inclusive and total-inelastic-reaction studies are discussed in terms of a simple model which assumes contributions to $〈n_X〉$ from the target-fragmentation, the central, and the beam-fragmentation regions in the case of total-inelastic reactions. For inclusive reactions, either the beam or target fragmentation is replaced by an exchange-particle-fragmentation contribution. The $s$, $t$, and ${M_X}^2$ dependence of the parameters of the model are deduced from triple-Regge considerations. The data are found to be consistent with the model and values are presented for the parameters.