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Title: A High Precision Measurement of the Proton Charge Radius at JLab

Abstract

The elastic electron-proton (e-p) scattering and the spectroscopy of hydrogen atoms are the two traditional methods to determine the proton charge radius (r p). In 2010, a new method using muonic hydrogen (µH) 1 spectroscopy reported a r p result that was nearly ten times more precise but significantly smaller than the values from the compilation of all previous r p measurements. This discrepancy is often referred to as the "proton charge radius puzzle". In order to investigate the puzzle, the PRad experiment (E12-11-106) was first proposed in 2011 and performed in 2016 in Hall B at the Thomas Jefferson National Accelerator Facility, with both 1.1 and 2.2 GeV electron beams. The experiment measured the e-p elastic scattering cross sections in an unprecedented low values of momentum transfer squared region (Q 2 = 2.1× 10 -4-0.06 (GeV/c) 2), with a sub-percent precision. The PRad experiment utilized a calorimetric method that was magnetic-spectrometer-free. Its detector setup included a large acceptance and high resolution calorimeter (HyCal), and two large-area, high spatial-resolution Gas Electron Multiplier (GEM) detectors. To have a better control over the systematic uncertainties, the absolute e-p elastic scattering cross section was normalized to that of the well-known Møller scattering process,more » which was measured simultaneously during the experiment. For each beam energy, all data with different Q 2 were collected simultaneously with the same detector setup, therefore sharing the same integrated luminosity. The windowless H 2 gas-flow target utilized in the experiment largely removed a typical background source, the target cell windows. The proton charge radius was determined as r p = 0.831±0.007 stat.±0.012 p fm, which is smaller than the average r p from previous e-p elastic scattering experiments, but in agreement with the µH spectroscopic results within the experimental uncertainties.« less

Authors:
Publication Date:
Research Org.:
Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Nuclear Physics (NP)
OSTI Identifier:
1673592
Report Number(s):
JLAB-PHY-20-3266; DOE/OR/23177-5059
DOE Contract Number:  
AC05-06OR23177
Resource Type:
Thesis/Dissertation
Country of Publication:
United States
Language:
English

Citation Formats

None, None. A High Precision Measurement of the Proton Charge Radius at JLab. United States: N. p., 2020. Web.
None, None. A High Precision Measurement of the Proton Charge Radius at JLab. United States.
None, None. Mon . "A High Precision Measurement of the Proton Charge Radius at JLab". United States. https://www.osti.gov/servlets/purl/1673592.
@article{osti_1673592,
title = {A High Precision Measurement of the Proton Charge Radius at JLab},
author = {None, None},
abstractNote = {The elastic electron-proton (e-p) scattering and the spectroscopy of hydrogen atoms are the two traditional methods to determine the proton charge radius (rp). In 2010, a new method using muonic hydrogen (µH)1 spectroscopy reported a rp result that was nearly ten times more precise but significantly smaller than the values from the compilation of all previous rp measurements. This discrepancy is often referred to as the "proton charge radius puzzle". In order to investigate the puzzle, the PRad experiment (E12-11-106) was first proposed in 2011 and performed in 2016 in Hall B at the Thomas Jefferson National Accelerator Facility, with both 1.1 and 2.2 GeV electron beams. The experiment measured the e-p elastic scattering cross sections in an unprecedented low values of momentum transfer squared region (Q2 = 2.1× 10-4-0.06 (GeV/c)2), with a sub-percent precision. The PRad experiment utilized a calorimetric method that was magnetic-spectrometer-free. Its detector setup included a large acceptance and high resolution calorimeter (HyCal), and two large-area, high spatial-resolution Gas Electron Multiplier (GEM) detectors. To have a better control over the systematic uncertainties, the absolute e-p elastic scattering cross section was normalized to that of the well-known Møller scattering process, which was measured simultaneously during the experiment. For each beam energy, all data with different Q2 were collected simultaneously with the same detector setup, therefore sharing the same integrated luminosity. The windowless H2 gas-flow target utilized in the experiment largely removed a typical background source, the target cell windows. The proton charge radius was determined as rp = 0.831±0.007stat.±0.012p fm, which is smaller than the average rp from previous e-p elastic scattering experiments, but in agreement with the µH spectroscopic results within the experimental uncertainties.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2020},
month = {2}
}

Thesis/Dissertation:
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