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Final SeaQuest Results on the Flavor Asymmetry of the Proton Light-Quark Sea with Proton-Induced Drell-Yan Process

C. H. Leung ^1,*,†, J. Dove¹, K. Nagai ^2,3,4,5, K. Nakano ^6,7, S. Prasad ^1,8, A. S. Tadepalli^9,†, C. A. Aidala ^10,2, J. Arrington ^8,‡, C. Ayuso¹⁰ et al. (FNAL E906/SeaQuest Collaboration)

C. Ayuso¹⁰, C. L. Barker¹¹, W. C. Chang ³, A. Chen ¹, D. C. Christian ¹², B. P. Dannowitz¹, L. El Fassi ^13,9, D. F. Geesaman ⁸, R. Gilman ⁹, Y. Goto ⁷, R. S. Guo¹⁴, L. Guo ^2,§, T. J. Hague ^11,†, R. J. Holt ^8,∥, M. F. Hossain ^15,6, L. D. Isenhower ¹¹, E. R. Kinney ¹⁶, A. Klein², D. Kleinjan ², P.-J. Lin ^16,3,17, K. Liu ², M. X. Liu², W. Lorenzon ¹⁰, R. E. McClellan ^1,¶, P. L. McGaughey², M. M. Medeiros⁸, Y. Miyachi ¹⁸, S. Miyasaka ⁴, D. H. Morton ¹⁰, K. Nakahara¹⁹, J. C. Peng ¹, A. J. R. Puckett^2,**, A. Pun¹⁵, B. J. Ramson ¹⁰, P. E. Reimer ⁸, J. G. Rubin ^8,10, F. Sanftl⁴, S. Sawada ²⁰, T. Sawada ¹⁰, M. B. C. Scott ^10,8,††, T.-A. Shibata ^4,7,‡‡, D.-S. Su ³, M. Teo ¹, R. Towell ¹¹, S. Uemura ^2,§§, S. G. Wang ^{3,14,12,∥∥}, J. Wu ¹², N. Wuerfel ¹⁰, and Z. H. Ye ^8,¶¶ (FNAL E906/SeaQuest Collaboration)

¹Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
²Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
³Institute of Physics, Academia Sinica, Taipei 11529, Taiwan
⁴Department of Physics, Tokyo Institute of Technology, Meguro-ku, Tokyo 152-8550, Japan
⁵Department of Physics and Materials Science, The University of Memphis, Memphis, Tennessee 38152, USA
⁶University of Virginia, Charlottesville, Virginia 22904, USA
⁷RIKEN Nishina Center for Accelerator-Based Science, Wako, Saitama 351-0198, Japan
⁸Physics Division, Argonne National Laboratory, Lemont, Illinois 60439, USA
⁹Department of Physics and Astronomy, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854, USA
¹⁰Randall Laboratory of Physics, University of Michigan, Ann Arbor, Michigan 48109, USA
¹¹Department of Engineering and Physics, Abilene Christian University, Abilene, Texas 79699, USA
¹²Fermi National Accelerator Laboratory, Batavia, Illinois 60510, USA
¹³Department of Physics and Astronomy, Mississippi State University, Mississippi State, Mississippi 39762, USA
¹⁴Department of Physics, National Kaohsiung Normal University, Kaohsiung 824, Taiwan
¹⁵Department of Physics, New Mexico State University, Las Cruces, New Mexico 88003, USA
¹⁶Department of Physics, University of Colorado, Boulder, Colorado 80309, USA
¹⁷Department of Physics, National Central University, Jhongli District, Taoyuan City 32001, Taiwan
¹⁸Department of Physics, Yamagata University, Yamagata City, Yamagata 990-8560, Japan
¹⁹Department of Physics, University of Maryland, College Park, Maryland 20742, USA
²⁰Institute of Particle and Nuclear Studies, KEK, High Energy Accelerator Research Organization, Tsukuba, Ibaraki 305-0801, Japan

^*Contact author: cleung@jlab.org
^†Present address: Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606, USA.
^‡Present address: Lawrence Berkeley National Laboratory, Berkeley, California 94720 USA.
^§Present address: Physics Department, Florida International University, Miami, Florida, 33199, USA.
^∥Present address: Kellogg Radiation Laboratory, California Institute of Technology, Pasadena, California 91125, USA.
^¶Present address: Pensacola State College, Pensacola, Florida 32504, USA.
^**Present address: University of Connecticut, Storrs, Connecticut 06269, USA.
^††Present address: George Washington University, Washington, DC 20052, USA.
^‡‡Present address: Nihon University, College of Science and Technology, Chiyoda-ku, Tokyo 101-8308, Japan.
^§§Present address: Fermi National Accelerator Laboratory, Batavia, Illinois 60510, USA.
^∥∥Present address: APS, Argonne National Laboratory, Lemont, Illinois 60439, USA.
^¶¶Present address: Department of Physics, Tsinghua University, Beijing 100084, China.

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Phys. Rev. Lett. 136, 171901 – Published 30 April, 2026

DOI: https://doi.org/10.1103/fdrg-gw3s

Abstract

The Fermilab E906/SeaQuest collaboration performed measurements of the Drell-Yan process using 120 GeV proton beams bombarding liquid hydrogen and liquid deuterium targets. A combined analysis of all collected data was performed to obtain the final results for the $σ_{p d} / 2 σ_{p p}$ Drell-Yan cross section ratio covering the kinematic region of $0.13 < x < 0.45$ . The $x$ dependencies of $\bar{d} (x) / \bar{u} (x)$ and $\bar{d} (x) - \bar{u} (x)$ are extracted from these cross section ratios. It is found that $\bar{d} (x)$ is greater than $\bar{u} (x)$ over the entire measured $x$ range, with improved statistical accuracy compared to previous measurements. The new results on $\bar{d} (x) / \bar{u} (x)$ and $\bar{d} (x) - \bar{u} (x)$ are compared to various parton distribution functions and theoretical calculations.

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Phys. Rev. Lett. 136, 171901– Published 30 April, 2026

Vol. 136, Iss. 17 — 1 May 2026

Received 8 January 2026
Revised 6 March 2026
Accepted 17 March 2026

DOI: https://doi.org/10.1103/fdrg-gw3s

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.

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Final SeaQuest Results on the Flavor Asymmetry of the Proton Light-Quark Sea with Proton-Induced Drell-Yan Process

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