Comparison of energy dependence of transverse momentum of dimuons produced inpNandπ−Ninteractions with quantum-chromodynamic predictions

We have analyzed the dependence of the average transverse momentum squared $〈{p_T}^2〉$ of dimuons produced in $\mathrm{pN}$ and ${\pi }^{-}N$ interactions on $s$, the square of the center-of-mass energy. The presently available data indicate a linear increase of $〈{p_T}^2〉$ with $s$ in both reactions, with the rate of increase being approximately twice as large in the ${\pi }^{-}N$ reaction for $\frac{M}{\sqrt{s}}=0.28\mathrm{}$ as in the $\mathrm{pN}$ reaction for $\frac{M}{\sqrt{s}}=0.22\mathrm{}$. The value of $〈{p_T}^2〉$ extrapolated to $s=0\mathrm{}$, which is interpreted as the intrinsic $〈{k_T}^2〉$ of the ${\pi }^{-}$ and $p$ constituents, is the same within errors for both reactions. First-order QCD consistently predicts a lower $〈{p_T}^2〉$ at all $s$ than is observed in the data.