The asymmetry of antimatter in the proton

J Dove¹, B Kerns¹, R E McClellan^{1

2}, S Miyasaka³, D H Morton⁴, K Nagai^{3

5}, S Prasad¹, F Sanftl³, M B C Scott⁴, A S Tadepalli^{6

2}, C A Aidala^{4

7}, J Arrington^{8

9}, C Ayuso^{4

10}, C L Barker¹¹, C N Brown¹², W C Chang⁵, A Chen^{1

4

5}, D C Christian¹³, B P Dannowitz¹, M Daugherity¹¹, M Diefenthaler^{1

2}, L El Fassi^{6

14}, D F Geesaman^{8

15}, R Gilman⁶, Y Goto¹⁶, L Guo^{7

17}, R Guo¹⁸, T J Hague¹¹, R J Holt^{8

19}, D Isenhower¹¹, E R Kinney²⁰, N Kitts¹¹, A Klein⁷, D W Kleinjan⁷, Y Kudo²¹, C Leung¹, P-J Lin²⁰, K Liu⁷, M X Liu⁷, W Lorenzon⁴, N C R Makins¹, M Mesquita de Medeiros⁸, P L McGaughey⁷, Y Miyachi²¹, I Mooney^{4

22}, K Nakahara^{23

24}, K Nakano^{3

16}, S Nara²¹, J-C Peng¹, A J Puckett^{7

25}, B J Ramson^{4

26}, P E Reimer²⁷, J G Rubin^{4

8}, S Sawada²⁸, T Sawada^{4

29}, T-A Shibata^{3

30}, D Su⁵, M Teo^{1

31}, B G Tice⁸, R S Towell¹¹, S Uemura^{7

32}, S Watson¹¹, S G Wang^{5

18

33}, A B Wickes⁷, J Wu¹³, Z Xi¹¹, Z Ye⁸

Affiliations

¹ Department of Physics, University of Illinois at Urbana-Champaign, Urbana, IL, USA.
² Experimental Nuclear Physics Division, Thomas Jefferson National Accelerator Facility, Newport News, VA, USA.
³ Department of Physics, School of Science, Tokyo Institute of Technology, Tokyo, Japan.
⁴ Randall Laboratory of Physics, University of Michigan, Ann Arbor, MI, USA.
⁵ Institute of Physics, Academia Sinica, Taipei, Taiwan.
⁶ Department of Physics and Astronomy, Rutgers, The State University of New Jersey, Piscataway, NJ, USA.
⁷ Physics Division, Los Alamos National Laboratory, Los Alamos, NM, USA.
⁸ Physics Division, Argonne National Laboratory, Lemont, IL, USA.
⁹ Physics Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.
¹⁰ Department of Physics, Mississippi State University, Mississippi State, MS, USA.
¹¹ Department of Engineering and Physics, Abilene Christian University, Abilene, TX, USA.
¹² Accelerator Division, Fermi National Accelerator Laboratory, Batavia, IL, USA.
¹³ Particle Physics Division, Fermi National Accelerator Laboratory, Batavia, IL, USA.
¹⁴ Department of Physics and Astronomy, Mississippi State University, Mississippi State, MS, USA.
¹⁵ Global Empire LLC, Lemont, IL, USA.
¹⁶ RIKEN Nishina Center for Accelerator-Based Science, Wako, Japan.
¹⁷ Department of Physics, Florida International University, Miami, FL, USA.
¹⁸ Department of Physics, National Kaohsiung Normal University, Kaohsiung, Taiwan.
¹⁹ Kellogg Radiation Laboratory, California Institute of Technology, Pasadena, CA, USA.
²⁰ Department of Physics, University of Colorado, Boulder, CO, USA.
²¹ Department of Physics, Yamagata University, Yamagata, Japan.
²² Department of Physics, Wayne State University, Detroit, MI, USA.
²³ Department of Physics, University of Maryland, College Park, MD, USA.
²⁴ Stanford Linear Accelerator Center, Menlo Park, CA, USA.
²⁵ Department of Physics, University of Connecticut, Storrs, CT, USA.
²⁶ Neutrino Division, Fermi National Accelerator Laboratory, Batavia, IL, USA.
²⁷ Physics Division, Argonne National Laboratory, Lemont, IL, USA. reimer@anl.gov.
²⁸ Institute of Particle and Nuclear Studies, KEK, High Energy Accelerator Research Organization, Tsukuba, Japan.
²⁹ Department of Physics, Osaka City University, Osaka City, Japan.
³⁰ Department of Physics, College of Science and Technology, Nihon University, Tokyo, Japan.
³¹ Department of Physics, Stanford University, Stanford, CA, USA.
³² Department of Physics, Tel Aviv University, Tel Aviv, Israel.
³³ Accelerator Systems Division, Argonne National Laboratory, Lemont, IL, USA.

PMID: 33627814
DOI: 10.1038/s41586-021-03282-z

Free article

The asymmetry of antimatter in the proton

J Dove et al. Nature. 2021 Feb.

Free article

. 2021 Feb;590(7847):561-565.

doi: 10.1038/s41586-021-03282-z. Epub 2021 Feb 24.

Authors

Affiliations

¹ Department of Physics, University of Illinois at Urbana-Champaign, Urbana, IL, USA.
² Experimental Nuclear Physics Division, Thomas Jefferson National Accelerator Facility, Newport News, VA, USA.
³ Department of Physics, School of Science, Tokyo Institute of Technology, Tokyo, Japan.
⁴ Randall Laboratory of Physics, University of Michigan, Ann Arbor, MI, USA.
⁵ Institute of Physics, Academia Sinica, Taipei, Taiwan.
⁶ Department of Physics and Astronomy, Rutgers, The State University of New Jersey, Piscataway, NJ, USA.
⁷ Physics Division, Los Alamos National Laboratory, Los Alamos, NM, USA.
⁸ Physics Division, Argonne National Laboratory, Lemont, IL, USA.
⁹ Physics Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.
¹⁰ Department of Physics, Mississippi State University, Mississippi State, MS, USA.
¹¹ Department of Engineering and Physics, Abilene Christian University, Abilene, TX, USA.
¹² Accelerator Division, Fermi National Accelerator Laboratory, Batavia, IL, USA.
¹³ Particle Physics Division, Fermi National Accelerator Laboratory, Batavia, IL, USA.
¹⁴ Department of Physics and Astronomy, Mississippi State University, Mississippi State, MS, USA.
¹⁵ Global Empire LLC, Lemont, IL, USA.
¹⁶ RIKEN Nishina Center for Accelerator-Based Science, Wako, Japan.
¹⁷ Department of Physics, Florida International University, Miami, FL, USA.
¹⁸ Department of Physics, National Kaohsiung Normal University, Kaohsiung, Taiwan.
¹⁹ Kellogg Radiation Laboratory, California Institute of Technology, Pasadena, CA, USA.
²⁰ Department of Physics, University of Colorado, Boulder, CO, USA.
²¹ Department of Physics, Yamagata University, Yamagata, Japan.
²² Department of Physics, Wayne State University, Detroit, MI, USA.
²³ Department of Physics, University of Maryland, College Park, MD, USA.
²⁴ Stanford Linear Accelerator Center, Menlo Park, CA, USA.
²⁵ Department of Physics, University of Connecticut, Storrs, CT, USA.
²⁶ Neutrino Division, Fermi National Accelerator Laboratory, Batavia, IL, USA.
²⁷ Physics Division, Argonne National Laboratory, Lemont, IL, USA. reimer@anl.gov.
²⁸ Institute of Particle and Nuclear Studies, KEK, High Energy Accelerator Research Organization, Tsukuba, Japan.
²⁹ Department of Physics, Osaka City University, Osaka City, Japan.
³⁰ Department of Physics, College of Science and Technology, Nihon University, Tokyo, Japan.
³¹ Department of Physics, Stanford University, Stanford, CA, USA.
³² Department of Physics, Tel Aviv University, Tel Aviv, Israel.
³³ Accelerator Systems Division, Argonne National Laboratory, Lemont, IL, USA.

PMID: 33627814
DOI: 10.1038/s41586-021-03282-z

Erratum in

Publisher Correction: The asymmetry of antimatter in the proton.
Dove J, Kerns B, McClellan RE, Miyasaka S, Morton DH, Nagai K, Prasad S, Sanftl F, Scott MBC, Tadepalli AS, Aidala CA, Arrington J, Ayuso C, Barker CL, Brown CN, Chang WC, Chen A, Christian DC, Dannowitz BP, Daugherity M, Diefenthaler M, El Fassi L, Geesaman DF, Gilman R, Goto Y, Guo L, Guo R, Hague TJ, Holt RJ, Isenhower D, Kinney ER, Kitts N, Klein A, Kleinjan DW, Kudo Y, Leung C, Lin PJ, Liu K, Liu MX, Lorenzon W, Makins NCR, de Medeiros MM, McGaughey PL, Miyachi Y, Mooney I, Nakahara K, Nakano K, Nara S, Peng JC, Puckett AJ, Ramson BJ, Reimer PE, Rubin JG, Sawada S, Sawada T, Shibata TA, Su D, Teo M, Tice BG, Towell RS, Uemura S, Watson S, Wang SG, Wickes AB, Wu J, Xi Z, Ye Z. Dove J, et al. Nature. 2022 Apr;604(7907):E26. doi: 10.1038/s41586-022-04707-z. Nature. 2022. PMID: 35396581 No abstract available.

Abstract

The fundamental building blocks of the proton-quarks and gluons-have been known for decades. However, we still have an incomplete theoretical and experimental understanding of how these particles and their dynamics give rise to the quantum bound state of the proton and its physical properties, such as its spin¹. The two up quarks and the single down quark that comprise the proton in the simplest picture account only for a few per cent of the proton mass, the bulk of which is in the form of quark kinetic and potential energy and gluon energy from the strong force². An essential feature of this force, as described by quantum chromodynamics, is its ability to create matter-antimatter quark pairs inside the proton that exist only for a very short time. Their fleeting existence makes the antimatter quarks within protons difficult to study, but their existence is discernible in reactions in which a matter-antimatter quark pair annihilates. In this picture of quark-antiquark creation by the strong force, the probability distributions as a function of momentum for the presence of up and down antimatter quarks should be nearly identical, given that their masses are very similar and small compared to the mass of the proton³. Here we provide evidence from muon pair production measurements that these distributions are considerably different, with more abundant down antimatter quarks than up antimatter quarks over a wide range of momenta. These results are expected to revive interest in several proposed mechanisms for the origin of this antimatter asymmetry in the proton that had been disfavoured by previous results⁴, and point to future measurements that can distinguish between these mechanisms.

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Comment in

Antimatter in the proton is more down than up.
Gao H. Gao H. Nature. 2021 Feb;590(7847):559-560. doi: 10.1038/d41586-021-00430-3. Nature. 2021. PMID: 33627805 No abstract available.

References

1. Ji, X., Yuan, F. & Zhao, Y. Proton spin after 30 years: what we know and what we don’t? Nat. Rev. Phys. 3, 27–38 (2021). - DOI
1. Yang, Y.-B. et al. Proton mass decomposition from the QCD energy momentum tensor. Phys. Rev. Lett. 121, 212001 (2018). - DOI
1. Ross, D. & Sachrajda, C. Flavour symmetry breaking in antiquark distributions. Nucl. Phys. B 149, 497–516 (1979). - DOI
1. Towell, R. S. et al. Improved measurement of the [Formula: see text] asymmetry in the nucleon sea. Phys. Rev. D 64, 052002 (2001). - DOI
1. Fermi, E. & Marshall, L. On the interaction between neutrons and electrons. Phys. Rev. 72, 1139–1146 (1947). - DOI

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The asymmetry of antimatter in the proton

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The asymmetry of antimatter in the proton

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