Study of opposite-sign dimuon production in high-energy neutrino-nucleon interactions

Results are presented of a study of opposite-sign dimuon events observed in a fine-grained neutrino detector exposed to the Fermilab Tevatron wide-band neutrino beam. A total of 300 background-corrected ${\mu }^{+}{\mu }^{-}$ events induced by incident neutrinos and antineutrinos with energies up to 500 GeV were accumulated. The data were analyzed in terms of a model based on charmquark production followed by semileptonic decay of the charmed meson. The Cabibbo-Kobayashi-Maskawa matrix terms were found to be ${\left|U_{\mathrm{cd}}\right|}^2=0.0378\mathrm{}\pm 0.0127 {\left(\mathrm{stat}\right)}_{-0.0082\mathrm{}}^{+0.0099\mathrm{}} \left(\mathrm{syst}\right)$, and $\kappa {\left|U_{\mathrm{cs}}\right|}^2=0.391\mathrm{}\pm 0.076 {\left(\mathrm{stat}\right)}_{-0.066\mathrm{}}^{+0.097\mathrm{}} \left(\mathrm{syst}\right)$. The ratio of the strange to nonstrange sea in the nucleon, $\kappa =\frac{2S}{(\overline{U}+\overline{D})}$, was measured to be 0.407±0.075 ${\mathrm{}\left(\mathrm{stat}\right)\mathrm{}}_{-0.069\mathrm{}}^{+0.103\mathrm{}}$ (syst).