Higher-twist effects in the reaction. pi. sup minus N r arrow. mu. sup +. mu. sup minus X at 253 GeV/ c

The distributions of quarks in the pion and nucleon are extracted from measurements of the reaction {pi}{sup {minus}}{ital N}{r arrow}{mu}{sup +}{mu}{sup {minus}}{ital X} at 253 GeV/{ital c} in a naive Drell-Yan analysis, as well as QCD-corrected analyses at leading-log and next-to-leading-log order. As {ital x}{sub {pi}}{r arrow}1 the pion structure function shows a term that varies as 1/{ital m}{sub {mu}{mu}}{sup 4}, which we interpret as a higher-twist effect. Additionally, the angular distribution of the {mu}{sup +} in the muon-pair rest frame tends towards sin{sup 2}{theta} as {ital x}{sub {pi}}{r arrow}1 and as {ital m}{sub {mu}{mu}}{r arrow}0 in a manner consistent with higher-twist effects. When the strongly mass-dependent higher-twist effects are included as part of the pion structure function, the nucleon structure function agrees well with leading-twist results from deeply inelastic lepton-hadron scattering. A significant advance of the present work is the extension of the analysis to low masses by the subtraction of the {ital J}/{psi} and {psi}{prime} resonances from the continuum. Our analysis covers the kinematic range 0.4{lt}{ital x}{sub {pi}}{lt}1.0 and 0.02{lt}{ital x}{sub {ital N}}{lt}0.33 with 3.0{lt}{ital m}{sub {mu}{mu}}{lt}8.55 GeV/{ital c}{sup 2}. Cross sections for {psi}{prime} producton are presented in an appendix.