Published September 2023 | Version Published
Journal Article Open

Measurement of flavor asymmetry of the light-quark sea in the proton with Drell-Yan dimuon production in 𝑝+𝑝 and 𝑝+𝑑 collisions at 120 GeV

Abstract

Evidence for a flavor asymmetry between the ‾𝑒 and ‾𝑑 quark distributions in the proton has been found in deep-inelastic scattering and Drell-Yan experiments. The pronounced dependence of this flavor asymmetry on π‘₯ (fraction of nucleon momentum carried by partons) observed in the Fermilab E866 Drell-Yan experiment suggested a drop of the ‾𝑑⁑(π‘₯)/‾𝑒⁑(π‘₯) ratio in the π‘₯>0.15 region. We report results from the SeaQuest Fermilab E906 experiment with improved statistical precision for ‾𝑑⁑(π‘₯)/‾𝑒⁑(π‘₯) in the large π‘₯ region up to π‘₯=0.45 using the 120 GeV proton beam. Two different methods for extracting the Drell-Yan cross section ratios, πœŽπ‘β’π‘‘/2β’πœŽπ‘β’π‘, from the SeaQuest data give consistent results. The ‾𝑑⁑(π‘₯)/‾𝑒⁑(π‘₯) ratios and the ‾𝑑⁑(π‘₯)−‾𝑒⁑(π‘₯) differences are deduced from these cross section ratios for 0.13<π‘₯<0.45. The SeaQuest and E866/NuSea ‾𝑑⁑(π‘₯)/‾𝑒⁑(π‘₯) ratios are in good agreement for the π‘₯≲0.25 region. The new SeaQuest data, however, show that ‾𝑑⁑(π‘₯) continues to be greater than ‾𝑒⁑(π‘₯) up to the highest π‘₯ value (π‘₯=0.45). The new results on ‾𝑑⁑(π‘₯)/‾𝑒⁑(π‘₯) and ‾𝑑⁑(π‘₯)−‾𝑒⁑(π‘₯) are compared with various parton distribution functions and theoretical calculations.

Copyright and License

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Funded by SCOAP3.

Acknowledgement

We thank G. T. Garvey for contributions to the early stages of this experiment. We also thank the Fermilab Accelerator Division and Particle Physics Division for their support of this experiment. This work was performed by the SeaQuest Collaboration, whose work was supported in part by the US Department of Energy under Grant No. DE-AC02-06CH11357, the US National Science Foundation under Grants No. PHY 1812340, No. PHY 2012926, No. PHY 1807338, No. PHY 2110229, No. PHY 2111046, and No. PHY 1506489; National Science and Technology Council of Taiwan (R.O.C.); the DP&A and ORED at Mississippi State University; the JSPS (Japan) KAKENHI through Grants No. 21244028, No. 25247037, No. 25800133, No. 20K04000, and No. 22H01244; the Bilateral Programs Joint Research Projects of JSPS; the Tokyo Tech Global COE Program, Japan; the Yamada Science Foundation of Japan; and the Ministry of Science and Technology (MOST) of Taiwan. Fermilab is managed by Fermi Research Alliance, LLC (FRA), acting under Contract No. DE-AC02-07CH11359.

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Additional details

Identifiers

ISSN
2469-9993

Funding

United States Department of Energy
DE-AC02-06CH11357
National Science Foundation
PHY 1812340
National Science Foundation
PHY 2012926
National Science Foundation
PHY 1807338
National Science Foundation
PHY 2110229
National Science Foundation
PHY 2111046
National Science Foundation
PHY 1506489
National Science and Technology Council
Mississippi State University
Japan Society for the Promotion of Science
21244028
Japan Society for the Promotion of Science
25247037
Japan Society for the Promotion of Science
25800133
Japan Society for the Promotion of Science
20K04000
Japan Society for the Promotion of Science
22H01244
National Science and Technology Council
Fermi National Accelerator Laboratory
DE-AC02-07CH11359

Dates

Accepted
2023-07-11
Accepted
Available
2023-09-06
Published online

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Publication Status
Published