d/u Asymmetry in the Nucleon Sea
Fermilab E866 has performed a precise measurement of the ratio of Drell-Yan yields from an 800 GeV/c proton beam incident on hydrogen and deuterium targets, leading to the first determinations of {bar d}/{bar u} and {bar d}-{bar u} in the proton as functions of {chi}. The results show that {bar d} > {bar u} over a broad range of {chi} and provide valuable information regarding the origins of the {bar d}/{bar u} asymmetry and the antiquark sea in the nucleon. No known symmetry requires equality of the {bar d} and {bar u} distributions in the proton. However, until recently it had been generally assumed that {bar d}({chi}) {approx} {bar u}({chi}), where {chi} is the fraction of the proton's momentum (Bjorken-{chi}) carried by the antiquark, based both on the assumption that the majority of the antiquark sea in the nucleon originates from gluon splitting into q - {bar q} pairs and the lack of experimental evidence to the contrary. The first clear evidence that {bar d} {ne} {bar u} came from the NMC measurements of the structure functions F{sub 2}{sup p}({chi}) and F{sub 2}{sup n}({chi}) in deep-inelastic muon scattering on hydrogen and deuterium.
- Research Organization:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
- Sponsoring Organization:
- USDOE Office of Science (US)
- DOE Contract Number:
- AC05-00OR22725
- OSTI ID:
- 771522
- Report Number(s):
- P00-106676; TRN: US0100516
- Resource Relation:
- Conference: International Nuclear Physics Conference (INPC/98), Paris (FR), 08/24/1998--08/28/1998; Other Information: PBD: 24 Aug 1998
- Country of Publication:
- United States
- Language:
- English
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