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Measurement of parity violation in electron–quark scattering

Nature volume 506, pages 67–70 (2014)Cite this article

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Abstract

Symmetry permeates nature and is fundamental to all laws of physics. One example is parity (mirror) symmetry, which implies that flipping left and right does not change the laws of physics. Laws for electromagnetism, gravity and the subatomic strong force respect parity symmetry, but the subatomic weak force does not1,2. Historically, parity violation in electron scattering has been important in establishing (and now testing) the standard model of particle physics. One particular set of quantities accessible through measurements of parity-violating electron scattering are the effective weak couplings C2q, sensitive to the quarks’ chirality preference when participating in the weak force, which have been measured directly3,4 only once in the past 40 years. Here we report a measurement of the parity-violating asymmetry in electron–quark scattering, which yields a determination of 2C2u − C2d (where u and d denote up and down quarks, respectively) with a precision increased by a factor of five relative to the earlier result. These results provide evidence with greater than 95 per cent confidence that the C2q couplings are non-zero, as predicted by the electroweak theory. They lead to constraints on new parity-violating interactions beyond the standard model, particularly those due to quark chirality. Whereas contemporary particle physics research is focused on high-energy colliders such as the Large Hadron Collider, our results provide specific chirality information on electroweak theory that is difficult to obtain at high energies. Our measurement is relatively free of ambiguity in its interpretation, and opens the door to even more precise measurements in the future.

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Figure 1: Comparison of the present results with those of earlier experiments and predictions of the standard model.
Figure 2: Mass exclusion limits Λ on the electron and quark compositeness and contact interactions.

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Acknowledgements

We thank the personnel of Jefferson Lab for their efforts which resulted in the successful completion of the experiment, and A. Accardi, P. Blunden, W. Melnitchouk and their collaborators for carrying out the calculations necessary for the completion of the data analysis. X.Z. thanks the Medium Energy Physics Group at the Argonne National Laboratory for support during the initial work on this experiment. J.E. was supported by PAPIIT (DGAPAUNAM) project IN106913 and CONACyT (México) project 151234, and acknowledges the hospitality and support by the Mainz Institute for Theoretical Physics (MITP) where part of his work was completed. This work was supported in part by the Jeffress Memorial Trust (award no. J-836), the US NSF (award no. 0653347), and the US DOE (award nos DE-SC0003885 and DE-AC02-06CH11357). This work was authored by Jefferson Science Associates, LLC under US DOE contract no. DE-AC05-06OR23177. The US Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce this manuscript for US Government purposes.

Author information

Author notes

  1. Present addresses: Richland College, Dallas County Community College District, Dallas, Texas 75243, USA (R.S.); College of William and Mary, Williamsburg, Virginia 23187, USA (W.D.); Idaho State University, Pocatello, Idaho 83201, USA (D.M.); Rutgers, The State University of New Jersey, Newark, New Jersey 07102, USA (K.E.M.); Kasetsart University, Bangkok 10900, Thailand (K.S.).

  2. A. Saha: Deceased.

Authors and Affiliations

  1. University of Virginia, Charlottesville, 22904, Virginia, USA

    D. Wang, R. Subedi, X. Deng, G. D. Cates, M. M. Dalton, C. W. de Jager, D. Jones, N. Liyanage, V. Nelyubin, K. D. Paschke, S. Riordan, K. Saenboonruang, R. Silwal, W. A. Tobias & X. Zheng

  2. Massachusetts Institute of Technology, Cambridge, 02139, Massachusetts, USA

    K. Pan, W. Bertozzi, W. Deconinck, S. Gilad, J. Huang, S. Kowalski, N. Muangma & V. Sulkosky

  3. Syracuse University, Syracuse, 13244, New York, USA

    Z. Ahmed, R. Holmes, C. M. Jen, A. Rakhman & P. A. Souder

  4. University of Kentucky, Lexington, 40506, Kentucky, USA

    K. Allada & C. Dutta

  5. California State University, Los Angeles, Los Angeles, California 90032, USA.,

    K. A. Aniol & D. J. Margaziotis

  6. College of William and Mary, Williamsburg, 23187, Virginia, USA

    D. S. Armstrong, J. H. Lee & B. Zhao

  7. Physics Division, Argonne National Laboratory, Argonne, 60439, Illinois, USA

    J. Arrington, K. Hafidi, R. J. Holt, P. E. Reimer & J. Rubin

  8. Istituto Nazionale di Fisica Nucleare, Dipt. di Fisica dell'Univ. di Catania, I-95123 Catania, Italy.,

    V. Bellini, A. Giusa, G. Russo & C. M. Sutera

  9. Ohio University, Athens, 45701, Ohio, USA

    R. Beminiwattha, P. M. King, J. H. Lee, J. Roche & B. Waidyawansa

  10. Thomas Jefferson National Accelerator Facility, Newport News, 23606, Virginia, USA

    J. Benesch, A. Camsonne, J.-P. Chen, E. Chudakov, C. W. de Jager, A. Deur, J.-O. Hansen, D. W. Higinbotham, J. J. LeRose, D. G. Meekins, R. Michaels, S. Nanda, A. Saha, B. Sawatzky, R. Suleiman & B. Wojtsekhowski

  11. Carnegie Mellon University, Pittsburgh, 15213, Pennsylvania, USA

    F. Benmokhtar, G. B. Franklin, M. Friend, D. Parno & B. Quinn

  12. Old Dominion University, Norfolk, 23529, Virginia, USA

    M. Canan, S. Golge & C. E. Hyde

  13. INFN, Sezione di Roma, gruppo Sanità and Istituto Superiore di Sanità, I-00161 Rome, Italy.,

    E. Cisbani, S. Frullani & F. Garibaldi

  14. Università di Bari, I-70126 Bari, Italy.,

    R. De Leo

  15. Rutgers, The State University of New Jersey, Newark, 07102, New Jersey, USA

    L. El Fassi

  16. Instituto de Física, Universidad Nacional Autónoma de México, 04510 México D.F., Mexico.,

    J. Erler

  17. Temple University, Philadelphia, 19122, Pennsylvania, USA

    D. Flay & Z.-E. Meziani

  18. Kharkov Institute of Physics and Technology, Kharkov 61108, Ukraine.,

    A. Glamazdin

  19. Louisiana Technical University, Ruston, 71272, Louisiana, USA

    K. Grimm

  20. Longwood University, Farmville, 23909, Virginia, USA

    T. Holmstrom & K. Rider

  21. Clermont Université, Université Blaise Pascal, CNRS/IN2P3, Laboratoire de Physique Corpusculaire, FR-63000 Clermont-Ferrand, France.,

    C. E. Hyde

  22. Seoul National University, Seoul 151-742, South Korea.,

    Hoyoung Kang & Y. Oh

  23. University of Massachusetts Amherst, Amherst, 01003, Massachusetts, USA

    K. S. Kumar, D. McNulty & L. Mercado

  24. Kent State University, Kent, 44242, Ohio, USA

    E. Long

  25. INFN, Sezione di Roma and Sapienza — Università di Roma, I-00161 Rome, Italy.,

    F. Meddi & G. M. Urciuoli

  26. Institut Jožef Stefan, SI-1001 Ljubljana, Slovenia.,

    M. Mihovilovic & S. Sirca

  27. George Washington University, 20052, Washington DC, USA

    K. E. Myers

  28. Mississippi State University, Starkeville, 39762, Mississippi, USA

    A. Narayan &  Nuruzzaman

  29. University of New Hampshire, Durham, 03824, New Hampshire, USA

    S. K. Phillips

  30. Duke University, Durham, 27708, North Carolina, USA

    X. Qian & Y. Qiang

  31. Yerevan Physics Institute, Yerevan 0036, Armenia.,

    A. Shahinyan

  32. China Institute of Atomic Energy, Beijing 102413, China.,

    L. Ye

Consortia

The Jefferson Lab PVDIS Collaboration

  • D. Wang
  • , K. Pan
  • , R. Subedi
  • , X. Deng
  • , Z. Ahmed
  • , K. Allada
  • , K. A. Aniol
  • , D. S. Armstrong
  • , J. Arrington
  • , V. Bellini
  • , R. Beminiwattha
  • , J. Benesch
  • , F. Benmokhtar
  • , W. Bertozzi
  • , A. Camsonne
  • , M. Canan
  • , G. D. Cates
  • , J.-P. Chen
  • , E. Chudakov
  • , E. Cisbani
  • , M. M. Dalton
  • , C. W. de Jager
  • , R. De Leo
  • , W. Deconinck
  • , A. Deur
  • , C. Dutta
  • , L. El Fassi
  • , J. Erler
  • , D. Flay
  • , G. B. Franklin
  • , M. Friend
  • , S. Frullani
  • , F. Garibaldi
  • , S. Gilad
  • , A. Giusa
  • , A. Glamazdin
  • , S. Golge
  • , K. Grimm
  • , K. Hafidi
  • , J.-O. Hansen
  • , D. W. Higinbotham
  • , R. Holmes
  • , T. Holmstrom
  • , R. J. Holt
  • , J. Huang
  • , C. E. Hyde
  • , C. M. Jen
  • , D. Jones
  • , Hoyoung Kang
  • , P. M. King
  • , S. Kowalski
  • , K. S. Kumar
  • , J. H. Lee
  • , J. J. LeRose
  • , N. Liyanage
  • , E. Long
  • , D. McNulty
  • , D. J. Margaziotis
  • , F. Meddi
  • , D. G. Meekins
  • , L. Mercado
  • , Z.-E. Meziani
  • , R. Michaels
  • , M. Mihovilovic
  • , N. Muangma
  • , K. E. Myers
  • , S. Nanda
  • , A. Narayan
  • , V. Nelyubin
  • ,  Nuruzzaman
  • , Y. Oh
  • , D. Parno
  • , K. D. Paschke
  • , S. K. Phillips
  • , X. Qian
  • , Y. Qiang
  • , B. Quinn
  • , A. Rakhman
  • , P. E. Reimer
  • , K. Rider
  • , S. Riordan
  • , J. Roche
  • , J. Rubin
  • , G. Russo
  • , K. Saenboonruang
  • , A. Saha
  • , B. Sawatzky
  • , A. Shahinyan
  • , R. Silwal
  • , S. Sirca
  • , P. A. Souder
  • , R. Suleiman
  • , V. Sulkosky
  • , C. M. Sutera
  • , W. A. Tobias
  • , G. M. Urciuoli
  • , B. Waidyawansa
  • , B. Wojtsekhowski
  • , L. Ye
  • , B. Zhao
  •  & X. Zheng

Contributions

Authors contributed to one or more of the following areas: proposing, leading, and running the experiment; design, construction, optimization, and testing of the data acquisition system; data analysis; simulation; extraction of the physics results from measured asymmetries; and the writing of this Letter.

Corresponding author

Correspondence to X. Zheng.

Ethics declarations

Competing interests

The author declare no competing financial interests.

Additional information

J.E. is currently on sabbatical leave at the PRISMA Cluster of Excellence and MITP, Johannes Gutenberg University.

Supplementary information

Supplementary Information

This file contains Supplementary Methods, Supplementary References and Supplementary Tables 1-2. (PDF 244 kb)

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The Jefferson Lab PVDIS Collaboration. Measurement of parity violation in electron–quark scattering. Nature 506, 67–70 (2014). https://doi.org/10.1038/nature12964

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  • DOI: https://doi.org/10.1038/nature12964

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