QCD in the Limit xF → 1 as Studied in the Reaction π^- N → µ ⁺ µ ^- X

Abstract

In Fermilab experiment E 615 we^l have measured the production of high-mass muon pairs with 80- and 252-GeV pion beams. The relatively large momentum of quarks in pions allows us the study the QCD subprocess $q\overline{q}$ → µ ⁺ µ ⁻ in the kinematic limit $x_{\pi }^{\overline{q}}$ → 1. The data are consistent with many of the features of a higher-twist analysis, particulary the departure of the muon-pair angular distribution from the standard form 1+cos² θ _t . Analysis of J/ψ) and ψ’ production in the same data sample gives further evidence for interesting effects as xF → 1, which we attribute to the process $q\overline{q}$ → $c\overline{c}$.