Experimental study of muon pairs produced by 252-GeV pions on tungsten

We present the results of a study of muon pairs with invariant masses greater than 4.05 GeV/$c^2$ produced in high-energy pion-nucleon interactions. The production cross section together with the inferred pion and nucleon structure functions are reported and compared with other experiments and with QCD predictions. The transverse-momentum distributions are also presented. Finally, the full angular distribution in cosθ and φ is given as a function of mass, Feynman x, and transverse momentum. Longitudinal photon polarization is seen in the lower portion of the mass range at high $x_{\pi }$. This result is compared with a higher-twist model.