skip to main content
DOE PAGES title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: A small proton charge radius from an electron–proton scattering experiment

Abstract

Elastic electron–proton scattering (e–p) and the spectroscopy of hydrogen atoms are the two methods traditionally used to determine the proton charge radius, rp. In 2010, a new method using muonic hydrogen atoms found a substantial discrepancy compared with previous results, which became known as the ‘proton radius puzzle’. Despite experimental and theoretical efforts, the puzzle remains unresolved. In fact, there is a discrepancy between the two most recent spectroscopic measurements conducted on ordinary hydrogen. Here we report on the proton charge radius experiment at Jefferson Laboratory (PRad), a high-precision e–p experiment that was established after the discrepancy was identified. We used a magnetic-spectrometer-free method along with a windowless hydrogen gas target, which overcame several limitations of previous e–p experiments and enabled measurements at very small forward-scattering angles. Our result, rp = 0.831 ± 0.007stat ± 0.012syst femtometres, is smaller than the most recent high-precision e–p measurement and 2.7 standard deviations smaller than the average of all e–p experimental results. Here, the smaller rp we have now measured supports the value found by two previous muonic hydrogen experiments. In addition, our finding agrees with the revised value (announced in 2019) for the Rydberg constant—one of the most accurately evaluated fundamental constantsmore » in physics.« less

Authors:
 [1];  [2];  [1];  [3];  [4];  [5];  [6];  [1];  [5];  [3];  [5];  [1];  [2];  [1];  [6];  [1];  [7];  [3];  [2];  [3] more »;  [3];  [6];  [6];  [6];  [6];  [5];  [3];  [3];  [3];  [3];  [8];  [9];  [3];  [3];  [6];  [10];  [11];  [12];  [1];  [13];  [6];  [6];  [13];  [5];  [5];  [2];  [14];  [6];  [15];  [3];  [16];  [10];  [6];  [3];  [17];  [5];  [1];  [1] « less
  1. Duke Univ., Durham, NC (United States)
  2. North Carolina A & T State Univ., Greensboro, NC (United States)
  3. Mississippi State Univ., Mississippi State, MS (United States)
  4. Idaho State Univ., Pocatello, ID (United States)
  5. Univ. of Virginia, Charlottesville, VA (United States)
  6. Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
  7. Duke Univ., Durham, NC (United States); Argonne National Lab. (ANL), Argonne, IL (United States)
  8. Univ. of North Carolina, Wilmington, NC (United States)
  9. National Academy of Sciences of Ukraine (NASU), Kharkov (Ukraine). National Scientific Centre, Kharkov Inst. of Physics and Technology (KIPT)
  10. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
  11. Old Dominion Univ., Norfolk, VA (United States)
  12. National Research Centre (NRC), Moscow (Russian Federation). Kurchatov Inst. (NRCKI); Univ. of Massachusetts, Amherst, MA (United States)
  13. Hampton Univ., Hampton, VA (United States)
  14. College of William and Mary, Williamsburg, VA (United States)
  15. Norfolk State Univ., Norfolk, VA (United States)
  16. Yerevan Physics Inst. (YerPhI) (Armenia)
  17. National Research Centre (NRC), Moscow (Russian Federation). Kurchatov Inst. (NRCKI)
Publication Date:
Research Org.:
Mississippi State Univ., Mississippi State, MS (United States); Duke Univ., Durham, NC (United States); Argonne National Lab. (ANL), Argonne, IL (United States); Univ. of Massachusetts, Amherst, MA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Nuclear Physics (NP); National Science Foundation (NSF); USDOE Office of Science (SC), Basic Energy Sciences (BES)
OSTI Identifier:
1599193
Alternate Identifier(s):
OSTI ID: 1577255; OSTI ID: 1659122
Grant/Contract Number:  
FG02-07ER41528; FG02-03ER41231; PHY-1229153; AC02-06CH11357; FG02-88ER40415
Resource Type:
Accepted Manuscript
Journal Name:
Nature (London)
Additional Journal Information:
Journal Name: Nature (London); Journal Volume: 575; Journal Issue: 7781; Journal ID: ISSN 0028-0836
Publisher:
Nature Publishing Group
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; proton charge radius; 72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS

Citation Formats

Xiong, W., Gasparian, A., Gao, H., Dutta, D., Khandaker, M., Liyanage, N., Pasyuk, E., Peng, C., Bai, X., Ye, L., Gnanvo, K., Gu, C., Levillain, M., Yan, X., Higinbotham, D. W., Meziane, M., Ye, Z., Adhikari, K., Aljawrneh, B., Bhatt, H., Bhetuwal, D., Brock, J., Burkert, V., Carlin, C., Deur, A., Di, D., Dunne, J., Ekanayaka, P., El-Fassi, L., Emmich, B., Gan, L., Glamazdin, O., Kabir, M. L., Karki, A., Keith, C., Kowalski, S., Lagerquist, V., Larin, I., Liu, T., Liyanage, A., Maxwell, J., Meekins, D., Nazeer, S. J., Nelyubin, V., Nguyen, H., Pedroni, R., Perdrisat, C., Pierce, J., Punjabi, V., Shabestari, M., Shahinyan, A., Silwal, R., Stepanyan, S., Subedi, A., Tarasov, V. V., Ton, N., Zhang, Y., and Zhao, Z. W. A small proton charge radius from an electron–proton scattering experiment. United States: N. p., 2019. Web. https://doi.org/10.1038/s41586-019-1721-2.
Xiong, W., Gasparian, A., Gao, H., Dutta, D., Khandaker, M., Liyanage, N., Pasyuk, E., Peng, C., Bai, X., Ye, L., Gnanvo, K., Gu, C., Levillain, M., Yan, X., Higinbotham, D. W., Meziane, M., Ye, Z., Adhikari, K., Aljawrneh, B., Bhatt, H., Bhetuwal, D., Brock, J., Burkert, V., Carlin, C., Deur, A., Di, D., Dunne, J., Ekanayaka, P., El-Fassi, L., Emmich, B., Gan, L., Glamazdin, O., Kabir, M. L., Karki, A., Keith, C., Kowalski, S., Lagerquist, V., Larin, I., Liu, T., Liyanage, A., Maxwell, J., Meekins, D., Nazeer, S. J., Nelyubin, V., Nguyen, H., Pedroni, R., Perdrisat, C., Pierce, J., Punjabi, V., Shabestari, M., Shahinyan, A., Silwal, R., Stepanyan, S., Subedi, A., Tarasov, V. V., Ton, N., Zhang, Y., & Zhao, Z. W. A small proton charge radius from an electron–proton scattering experiment. United States. https://doi.org/10.1038/s41586-019-1721-2
Xiong, W., Gasparian, A., Gao, H., Dutta, D., Khandaker, M., Liyanage, N., Pasyuk, E., Peng, C., Bai, X., Ye, L., Gnanvo, K., Gu, C., Levillain, M., Yan, X., Higinbotham, D. W., Meziane, M., Ye, Z., Adhikari, K., Aljawrneh, B., Bhatt, H., Bhetuwal, D., Brock, J., Burkert, V., Carlin, C., Deur, A., Di, D., Dunne, J., Ekanayaka, P., El-Fassi, L., Emmich, B., Gan, L., Glamazdin, O., Kabir, M. L., Karki, A., Keith, C., Kowalski, S., Lagerquist, V., Larin, I., Liu, T., Liyanage, A., Maxwell, J., Meekins, D., Nazeer, S. J., Nelyubin, V., Nguyen, H., Pedroni, R., Perdrisat, C., Pierce, J., Punjabi, V., Shabestari, M., Shahinyan, A., Silwal, R., Stepanyan, S., Subedi, A., Tarasov, V. V., Ton, N., Zhang, Y., and Zhao, Z. W. Wed . "A small proton charge radius from an electron–proton scattering experiment". United States. https://doi.org/10.1038/s41586-019-1721-2. https://www.osti.gov/servlets/purl/1599193.
@article{osti_1599193,
title = {A small proton charge radius from an electron–proton scattering experiment},
author = {Xiong, W. and Gasparian, A. and Gao, H. and Dutta, D. and Khandaker, M. and Liyanage, N. and Pasyuk, E. and Peng, C. and Bai, X. and Ye, L. and Gnanvo, K. and Gu, C. and Levillain, M. and Yan, X. and Higinbotham, D. W. and Meziane, M. and Ye, Z. and Adhikari, K. and Aljawrneh, B. and Bhatt, H. and Bhetuwal, D. and Brock, J. and Burkert, V. and Carlin, C. and Deur, A. and Di, D. and Dunne, J. and Ekanayaka, P. and El-Fassi, L. and Emmich, B. and Gan, L. and Glamazdin, O. and Kabir, M. L. and Karki, A. and Keith, C. and Kowalski, S. and Lagerquist, V. and Larin, I. and Liu, T. and Liyanage, A. and Maxwell, J. and Meekins, D. and Nazeer, S. J. and Nelyubin, V. and Nguyen, H. and Pedroni, R. and Perdrisat, C. and Pierce, J. and Punjabi, V. and Shabestari, M. and Shahinyan, A. and Silwal, R. and Stepanyan, S. and Subedi, A. and Tarasov, V. V. and Ton, N. and Zhang, Y. and Zhao, Z. W.},
abstractNote = {Elastic electron–proton scattering (e–p) and the spectroscopy of hydrogen atoms are the two methods traditionally used to determine the proton charge radius, rp. In 2010, a new method using muonic hydrogen atoms found a substantial discrepancy compared with previous results, which became known as the ‘proton radius puzzle’. Despite experimental and theoretical efforts, the puzzle remains unresolved. In fact, there is a discrepancy between the two most recent spectroscopic measurements conducted on ordinary hydrogen. Here we report on the proton charge radius experiment at Jefferson Laboratory (PRad), a high-precision e–p experiment that was established after the discrepancy was identified. We used a magnetic-spectrometer-free method along with a windowless hydrogen gas target, which overcame several limitations of previous e–p experiments and enabled measurements at very small forward-scattering angles. Our result, rp = 0.831 ± 0.007stat ± 0.012syst femtometres, is smaller than the most recent high-precision e–p measurement and 2.7 standard deviations smaller than the average of all e–p experimental results. Here, the smaller rp we have now measured supports the value found by two previous muonic hydrogen experiments. In addition, our finding agrees with the revised value (announced in 2019) for the Rydberg constant—one of the most accurately evaluated fundamental constants in physics.},
doi = {10.1038/s41586-019-1721-2},
journal = {Nature (London)},
number = 7781,
volume = 575,
place = {United States},
year = {2019},
month = {11}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record

Citation Metrics:
Cited by: 23 works
Citation information provided by
Web of Science

Save / Share:

Works referenced in this record:

The size of the proton
journal, July 2010

  • Pohl, Randolf; Antognini, Aldo; Nez, François
  • Nature, Vol. 466, Issue 7303
  • DOI: 10.1038/nature09250

CODATA recommended values of the fundamental physical constants: 2006
journal, June 2008

  • Mohr, Peter J.; Taylor, Barry N.; Newell, David B.
  • Reviews of Modern Physics, Vol. 80, Issue 2
  • DOI: 10.1103/RevModPhys.80.633

The Rydberg constant and proton size from atomic hydrogen
journal, October 2017


New Measurement of the 1 S 3 S Transition Frequency of Hydrogen: Contribution to the Proton Charge Radius Puzzle
journal, May 2018


High-Precision Determination of the Electric and Magnetic Form Factors of the Proton
journal, December 2010


CODATA Recommended Values of the Fundamental Physical Constants: 2014
journal, December 2016

  • Mohr, Peter J.; Newell, David B.; Taylor, Barry N.
  • Journal of Physical and Chemical Reference Data, Vol. 45, Issue 4
  • DOI: 10.1063/1.4954402

Proton Structure from the Measurement of 2S-2P Transition Frequencies of Muonic Hydrogen
journal, January 2013


Computing the nucleon charge and axial radii directly at Q 2 = 0 in lattice QCD
journal, February 2018


CODATA recommended values of the fundamental physical constants: 2010
journal, November 2012


The proton radius puzzle
journal, May 2015


Defining the proton radius: A unified treatment
journal, March 2019


Proton polarizability contribution: Muonic hydrogen Lamb shift and elastic scattering
journal, January 2013


Theory of the 2S–2P Lamb shift and 2S hyperfine splitting in muonic hydrogen
journal, April 2013


Extraction of the proton radius from electron-proton scattering data
journal, July 2015


Proton radius from electron scattering data
journal, May 2016


Consistency of electron scattering data with a small proton radius
journal, June 2016


A high Performance Hybrid Electromagnetic Calorimeter at Jefferson lab
conference, January 2012

  • Gasparian, A.
  • Proceedings of the Eleventh International Conference, Calorimetry in Particle Physics
  • DOI: 10.1142/9789812701978_0014

The CEBAF large acceptance spectrometer (CLAS)
journal, May 2003

  • Mecking, B. A.; Adams, G.; Ahmad, S.
  • Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, Vol. 503, Issue 3
  • DOI: 10.1016/S0168-9002(03)01001-5

Geant4—a simulation toolkit
journal, July 2003

  • Agostinelli, S.; Allison, J.; Amako, K.
  • Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, Vol. 506, Issue 3
  • DOI: 10.1016/S0168-9002(03)01368-8

A new event generator for the elastic scattering of charged leptons on protons
journal, September 2014

  • Gramolin, A. V.; Fadin, V. S.; Feldman, A. L.
  • Journal of Physics G: Nuclear and Particle Physics, Vol. 41, Issue 11
  • DOI: 10.1088/0954-3899/41/11/115001

Empirical fit to precision inclusive electron-proton cross sections in the resonance region
journal, May 2010


Simple parametrization of nucleon form factors
journal, December 2004


Realistic transverse images of the proton charge and magnetization densities
journal, January 2011


Robust extraction of the proton charge radius from electron-proton scattering data
journal, August 2018


Proton charge radius extraction from electron scattering data using dispersively improved chiral effective field theory
journal, April 2019


CODATA recommended values of the fundamental physical constants: 2006
journal, September 2008

  • Mohr, Peter J.; Taylor, Barry N.; Newell, David B.
  • Journal of Physical and Chemical Reference Data, Vol. 37, Issue 3
  • DOI: 10.1063/1.2844785

    Works referencing / citing this record:

    Hyperfine structure of P states in muonic ions of lithium, beryllium, and boron
    journal, December 2019


    Muonic Lithium atoms: nuclear structure corrections to the Lamb shift
    journal, January 2020