Average charged-particle multiplicities in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msup><mml:mrow><mml:mi>π</mml:mi></mml:mrow><mml:mrow><mml:mo>−</mml:mo></mml:mrow></mml:msup></mml:mrow><mml:mi>p</mml:mi></mml:math>inclusive reactions at 147 GeV/<i>c</i>

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 $|t|:{\ensuremath{\pi}}^{\ensuremath{-}}p\ensuremath{\rightarrow}{\ensuremath{\pi}}_{\mathrm{fast}}^{\ensuremath{-}}X$, ${\ensuremath{\pi}}^{\ensuremath{-}}p\ensuremath{\rightarrow}\mathrm{pX}$, ${\ensuremath{\pi}}^{\ensuremath{-}}p\ensuremath{\rightarrow}{\ensuremath{\Delta}}^{++}X$, ${\ensuremath{\pi}}^{\ensuremath{-}}p\ensuremath{\rightarrow}{({\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{+})}_{{\ensuremath{\rho}}^{0}}X$, and ${\ensuremath{\pi}}^{\ensuremath{-}}p\ensuremath{\rightarrow}{\ensuremath{\Lambda}}^{0}X$. Details of the analysis are discussed. These data can be fit by the expression $〈{n}_{X}〉=A+B \mathrm{ln} {{M}_{X}}^{2}+C|t|$ and the coefficients obtained for $B$ are equal within their uncertainties. $C$ is significantly different from zero only for ${\ensuremath{\pi}}^{\ensuremath{-}}p\ensuremath{\rightarrow}{\ensuremath{\pi}}_{\mathrm{fast}}^{\ensuremath{-}}X$. 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.