Nuclear dependence of high-xthadron and high-τ hadron-pair production inp-Ainteractions at √s=38.8 GeV

Abstract

We present a high-statistics, species-identified measurement of the W-to-Be per-nucleon cross-section ratio, ${\mathit{R}}_{\mathrm{W}/\mathrm{B}\mathrm{e}}$, for high-${\mathit{x}}_{\mathit{t}}$ hadrons and high-τ ${\mathit{h}}^{+}$ ${\mathit{h}}^{\mathrm{-}}$ pairs produced in p-A collisions at √s =38.8 GeV. The data extend to 0.62 in ${\mathit{x}}_{\mathit{t}}$ and 0.39 in √τ . For single hadrons, ${\mathit{R}}_{\mathrm{W}/\mathrm{B}\mathrm{e}}$ peaks at ${\mathit{p}}_{\mathit{t}}$≊5 GeV/c and decreases to ≊1 for mesons with pt>8 GeV/c. At fixed ${\mathit{p}}_{\mathit{t}}$, ${\mathit{R}}_{\mathrm{W}/\mathrm{B}\mathrm{e}}$ falls with √s . For symmetric pairs with √τ >0.28, ${\mathit{R}}_{\mathrm{W}/\mathrm{B}\mathrm{e}}$=0.84±0.02±0.07, suggesting a nuclear suppression of high-z fragmentation. ${\mathit{R}}_{\mathrm{W}/\mathrm{B}\mathrm{e}}$ increases with ${\mathit{p}}_{\mathrm{out}}$, indicative of constituent multiple scattering.