Absolute Drell-Yan Dimuon Cross Sections in 800 GeV/c pp and pd Collisions

Abstract

The Fermilab E866/NuSea Collaboration has measured the Drell-Yan dimuon cross sections in 800 GeV/$c$ $pp$ and $pd$ collisions. This represents the first measurement of the Drell-Yan cross section in $pp$ collisions over a broad kinematic region and the most extensive study to date of the Drell-Yan cross section in $pd$ collisions. The results indicate that recent global parton distribution fits provide a good description of the light antiquark sea in the nucleon over the Bjorken-$x$ range $0.03 \lesssim x < 0.15$, but overestimate the valence quark distributions as $x \to 1$.

Figures (2)

• Figure 1: FNAL E866 Drell-Yan cross sections per nucleon for selected $x_F$ bins. The E866 $pd$ (solid circles) and $pp$ (solid diamonds) cross sections are shown in alternate decades, compared with previous $p$Cu results from E605 e605 (open triangles) and $pd$ results from E772 e772 (open squares). NLO cross section calculations based on the CTEQ6 cteq6 (dashed curves) and MRST2001 mrst01 (solid curves) PDF fits are also shown. The error bars on the E605 and E772 data points are statistical only. Those on the E866 data points are the sum in quadrature of the statistical and point-to-point systematic uncertainties. An additional $\pm$ 6.5% normalization uncertainty is common to all E866 data points.
• Figure 2: Ratios of the measured Drell-Yan $pp$ (open triangles) and $pd$ (solid circles) cross sections to NLO calculations based on the MRST2001 mrst01 PDF fit plotted vs. a) $x_2$ and b) $x_1$, averaged over the other variable. The inner error bars represent the statistical uncertainty in the ratio, the outer error bar the sum in quadrature of the statistical and point-to-point systematic uncertainties. Solid lines represent the experimental uncertainty ranges mrst02 on a) $\bar{u}+\bar{d}$ and b) $4u+d$ in the MRST2001 PDF fit. Dashed and dot-dashed lines are the $pd$ and $pp$ fits described in the text.