Probing the flavor dependence of proton's light-quark sea in the SeaQuest experiment

Abstract

Surprisingly large flavor asymmetry of the light-quark sea in the proton was reported in deepinelastic scattering and Drell-Yan experiments. The Bjorken-x dependence of the d/ ū ratio extracted from the Fermilab E866 experiment also revealed an intriguing drop at the highest values of x. The Fermilab E906/SeaQuest experiment was designed to measure d/ ū with improved accuracy at high Bjorken-x. By detecting high-mass dimuon events produced in the interaction of 120 GeV proton beam with liquid hydrogen (LH 2 ) and deuterium (LD 2 ) targets, the SeaQuest experiment probes the d/ ū ratio up to x ≈ 0.45. Data collection has been completed and we report the status of data analysis for SeaQuest. Two different methods for extracting the LD 2 /LH 2 Drell-Yan cross section ratios for 0.1 ≤ x ≤ 0.45 are discussed. These ratios are compared with calculations using various PDFs.

On the flavor structure of the light-quark sea distributions

“…[7,8], the agreement is limited to x target < 0.2. On the same figure is shown the preliminary results of the SeaQuest E906 experiment at p lab = 120GeV [17] which are in better agreement with our model. The slow variation ofd/ū with Q 2 and the increase with x which come in our model from an analysis of a large set of experimental data implies a weak energy dependence of the ratio σ(pd)/2σ(pp), so the rapid decrease of the E866 experiment above x target > 0.2 is really unexpected.…”