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A small proton charge radius from an electron-proton scattering experiment.

Publication ,  Journal Article
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 ...
Published in: Nature
November 2019

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 atoms1 found a substantial discrepancy compared with previous results2, 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 hydrogen3,4. 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 measurement5 and 2.7 standard deviations smaller than the average of all e-p experimental results6. The smaller rp we have now measured supports the value found by two previous muonic hydrogen experiments1,7. In addition, our finding agrees with the revised value (announced in 2019) for the Rydberg constant8-one of the most accurately evaluated fundamental constants in physics.

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Published In

Nature

DOI

EISSN

1476-4687

ISSN

0028-0836

Publication Date

November 2019

Volume

575

Issue

7781

Start / End Page

147 / 150

Related Subject Headings

  • General Science & Technology
 

Citation

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Xiong, W., Gasparian, A., Gao, H., Dutta, D., Khandaker, M., Liyanage, N., … Zhao, Z. W. (2019). A small proton charge radius from an electron-proton scattering experiment. Nature, 575(7781), 147–150. https://doi.org/10.1038/s41586-019-1721-2
Xiong, W., A. Gasparian, H. Gao, D. Dutta, M. Khandaker, N. Liyanage, E. Pasyuk, et al. “A small proton charge radius from an electron-proton scattering experiment.Nature 575, no. 7781 (November 2019): 147–50. https://doi.org/10.1038/s41586-019-1721-2.
Xiong W, Gasparian A, Gao H, Dutta D, Khandaker M, Liyanage N, et al. A small proton charge radius from an electron-proton scattering experiment. Nature. 2019 Nov;575(7781):147–50.
Xiong, W., et al. “A small proton charge radius from an electron-proton scattering experiment.Nature, vol. 575, no. 7781, Nov. 2019, pp. 147–50. Epmc, 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 DW, 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 ML, Karki A, Keith C, Kowalski S, Lagerquist V, Larin I, Liu T, Liyanage A, Maxwell J, Meekins D, Nazeer SJ, Nelyubin V, Nguyen H, Pedroni R, Perdrisat C, Pierce J, Punjabi V, Shabestari M, Shahinyan A, Silwal R, Stepanyan S, Subedi A, Tarasov VV, Ton N, Zhang Y, Zhao ZW. A small proton charge radius from an electron-proton scattering experiment. Nature. 2019 Nov;575(7781):147–150.
Journal cover image

Published In

Nature

DOI

EISSN

1476-4687

ISSN

0028-0836

Publication Date

November 2019

Volume

575

Issue

7781

Start / End Page

147 / 150

Related Subject Headings

  • General Science & Technology