Muon pair production in proton-nucleon interactions and new parton radiative processes

Abstract

An examination of experimental data bearing on the production of muon pairs in nucleon-nucleon interactions demonstrates the existence of a large continuum for pairs with invariant masses less than 1.0 GeV/c/sup 2/. The ratio of the pairs to the production of pions, I (..mu mu..)/I (..pi../sup 0/), is of the order of 5 x 10/sup -5/ in the fragmentation region. The production of the pairs obeys Feynman scaling in the fragmentation region; the cross sections d/sup 2/sigma/dm dx are nearly the same for the interactions of 28-GeV protons and 150-GeV protons and the assumption of scaling is consistent with less detailed measurements at 400 GeV over a region of Feynman x such that 0.15 < x < 0.6 and for values of the invariant mass m < or approx. = 1.0 GeV/c/sup 2/. The invariant-mass spectrum of this continuum varies with x; the mean mass changes from about 450 MeV/c/sup 2/ at x = 0.2 to about 700 MeV/c/sup 2/ for x approx. = 0.6. The dimuon production varies with the target nucleus as A/sup 2/3/ in an x region where meson production varies as A/sup 0.55/. The production is discussed in terms of parton bremsstrahlung, the annihilation of partonmore » pairs produced by the hadron interaction (the Bjorken-Weisberg process) and line broadening of rho-meson production.« less