Quantum-chromodynamic radiation and mean scaling for hadronic and current processes

Abstract

A recently proposed model for the longitudinal- and transverse-momentum distribution of quantum-chromodynamics (QCD) radiation is shown to lead naturally to mean scaling. Excellent agreement is found for the normalized momentum distribution in $\mathrm{pp}\to n\pi +X$ between our predictions and the data from 13 to 1500 GeV/c with $n$, the number of pions, varying from 4 to 26. We also show that $\mu$-pair production by hadrons exhibits the same transverse-momentum spectrum as do the hadrons produced in $e^{+}{e}^{-}$ annihilation. This transverse scaling in the mean in terms of the dimensionless variable $z_{\perp }=\frac{k_{\perp }}{〈k_{\perp }〉}$ is interpreted as reflecting the primary (soft-gluon) QCD radiation distribution. Again, very good agreement is found for these normalized distributions and our theoretical scaling curves.