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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, r p. 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, r p = 0.831 ± 0.007 stat ± 0.012 syst 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 r p 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 themore » most accurately evaluated fundamental constants in physics.« less

Authors:
 [1];  [2];  [1];  [3];  [4];  [5];  [6];  [1];  [5];  [3];  [5];  [1];  [2];  [1];  [6];  [1];  [1];  [3];  [2];  [3] more »;  [3];  [6];  [6];  [6];  [6];  [5];  [3];  [3];  [3];  [3];  [7];  [8];  [3];  [3];  [6];  [9];  [10];  [11];  [1];  [12];  [6];  [6];  [12];  [5];  [5];  [2];  [13];  [6];  [14];  [3];  [15];  [9];  [6];  [3];  [16];  [5];  [1];  [1] « less
  1. Duke Univ. and Triangle Univ. Nuclear Lab., 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. Univ. of North Carolina, Wilmington, NC (United States)
  8. Kharkov Inst. of Physics and Technology, Kharkov (Ukraine)
  9. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
  10. Old Dominion Univ., Norfolk, VA (United States)
  11. Alikhanov Inst. for Theoretical and Experimental Physics NRC “Kurchatov Institute”, Moscow (Russia); Univ. of Massachusetts, Amherst, MA (United States)
  12. Hampton Univ., Hampton, VA (United States)
  13. College of William and Mary, Williamsburg, VA (United States)
  14. Norfolk State Univ., Norfolk, VA (United States)
  15. Yerevan Physics Inst., Yerevan (Armenia)
  16. Alikhanov Inst. for Theoretical and Experimental Physics NRC “Kurchatov Institute”, Moscow (Russia)
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
National Science Foundation (NSF); USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1577255
Grant/Contract Number:  
AC02-06CH11357
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:
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. doi: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. doi: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. doi:10.1038/s41586-019-1721-2.
@article{osti_1577255,
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}
}

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