Improved measurement of the anti-d / anti-u asymmetry in the nucleon sea

Measurements of the ratio of Drell-Yan yields from an 800 \rm{GeV/c} proton beam incident on liquid hydrogen and deuterium targets are reported. Approximately 360,000 Drell-Yan muon pairs remained after all cuts on the data. From these data, the ratio of anti-down (

\bar{d}

) to anti-up (

\bar{u}

) quark distributions in the proton sea is determined over a wide range in Bjorken-

x

. These results confirm previous measurements by E866 and extend them to lower

x

. From these data,

(\bar{d}-\bar{u})

and

\int(\bar{d}-\bar{u})dx

are evaluated for 0.015<x<0.35. These results are compared with parameterizations of various parton distribution functions, models and experimental results from NA51, NMC, and HERMES.

Note:

17 pages, 15 figures

p nucleon: inclusive reaction
hydrogen: liquid
deuterium: liquid
muon: pair production
Drell-Yan process
nucleon: structure function
antiquark: sea
asymmetry: (up down)
momentum spectrum: parton
parametrization

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Figures(16)

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