Proton charge and magnetic rms radii from the elastic ep scattering data

Borisyuk, Dmitry

doi:10.1016/j.nuclphysa.2010.05.054

Cited by 32 publications

(32 citation statements)

References 25 publications

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“…Comparing our third value of the magnetic radius of the proton, r p M = 0.87 +0.02 −0.02 fm, to the values quoted by the PDG [88], we find that they are more consistent with r p M = 0.876 ± 0.010 ± 0.016 fm extracted in [86] and r p M = 0.854 ± 0.005 fm extracted in [87], than the A1 collaboration value of r p M = 0.777(13) stat. (9) syst.…”

Section: Discussionsupporting

confidence: 86%

Model independent extraction of the proton magnetic radius from electron scattering

2014

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We combine constraints from analyticity with experimental electron-proton scattering data to determine the proton magnetic radius without model-dependent assumptions on the shape of the form factor. We also study the impact of including electron-neutron scattering data, and ππ → NN data. Using representative datasets we find for a cut of Q 2 ≤ 0.5 GeV 2 , r p M = 0.91 +0.03 −0.06 ± 0.02 fm using just proton scattering data; r p M = 0.87 +0.04 −0.05 ± 0.01 fm adding neutron data; and r p M = 0.87 +0.02 −0.02 fm adding ππ data. We also extract the neutron magnetic radius from these data sets obtaining r n M = 0.89 +0.03 −0.03 fm from the combined proton, neutron, and ππ data.

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Section: Discussionsupporting

confidence: 86%

Model independent extraction of the proton magnetic radius from electron scattering

2014

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“…When fitting data up to large q, which requires many free parameters, a different approach is needed. Multi-parameter models such as the Padé form factors [15,91], polynomials or inverse polynomials of high order [90][91][92] or polynomials as a function of derived quantities [64,93,94] have been employed. Typically, the number of parameters is increased until the χ 2 per degree of freedom reaches a plateau.…”

Section: Types Of Parameterizations Usedmentioning

confidence: 99%

“…Typically, the number of parameters is increased until the χ 2 per degree of freedom reaches a plateau. Occasionally, the model dependence is estimated by generating and fitting pseudo-data and comparing the fit-results to the known input values [15,90,92,94]. 3.…”

Section: Types Of Parameterizations Usedmentioning

confidence: 99%

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Proton Charge Radius from Electron Scattering

Sick

2017

Atoms

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Abstract:The rms-radius R of the proton charge distribution is a fundamental quantity needed for precision physics. This radius, traditionally determined from elastic electron-proton scattering via the slope of the Sachs form factor G e (q 2 ) extrapolated to momentum transfer q 2 = 0, shows a large scatter. We discuss the approaches used to analyze the e-p data, partly redo these analyses in order to identify the sources of the discrepancies and explore alternative parameterizations. The problem lies in the model dependence of the parameterized G(q) needed for the extrapolation. This shape of G(q < q min ) is closely related to the shape of the charge density ρ(r) at large radii r, a quantity that is ignored in most analyses. When using our physics knowledge about this large-r density together with the information contained in the high-q data, the model dependence of the extrapolation is reduced, and different parameterizations of the pre-2010 data yield a consistent value for R = 0.887 ± 0.012 fm. This value disagrees with the more precise value 0.8409 ± 0.0004 fm determined from the Lamb shift in muonic hydrogen.

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“…All the different values of r p which have been published come from a re-analysis of the low-momentum scattering data, associated or not to high-momentum scattering data (e.g. [15,16]). The re-analysis considered by the Committee on Data for Science and Technology (CODATA) task group has been obtained by Sick [17].…”

Section: Experimental Determinations Of the Proton Charge Radius (A) mentioning

confidence: 99%

Is the proton radius a player in the redefinition of the International System of Units?

Nez

Antognini

Amaro

et al. 2011

Phil. Trans. R. Soc. A.

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International audienceIt is now recognized that the International System of Units (SI units) will be redefined in terms of fundamental constants, even if the date when this will occur is still under debate. Actually, the best estimate of fundamental constant values is given by a least-squares adjustment, carried out under the auspices of the Committee on Data for Science and Technology (CODATA) Task Group on Fundamental Constants. This adjustment provides a significant measure of the correctness and overall consistency of the basic theories and experimental methods of physics using the values of the constants obtained from widely differing experiments. The physical theories that underlie this adjustment are assumed to be valid, such as quantum electrodynamics (QED). Testing QED, one of the most precise theories is the aim of many accurate experiments. The calculations and the corresponding experiments can be carried out either on a boundless system, such as the electron magnetic moment anomaly, or on a bound system, such as atomic hydrogen. The value of fundamental constants can be deduced from the comparison of theory and experiment. For example, using QED calculations, the value of the fine structure constant given by the CODATA is mainly inferred from the measurement of the electron magnetic moment anomaly carried out by Gabrielse's group. (Hanneke et al. 2008 Phys. Rev. Lett. 100, 120801) The value of the Rydberg constant is known from two-photon spectroscopy of hydrogen combined with accurate theoretical quantities. The Rydberg constant, determined by the comparison of theory and experiment using atomic hydrogen, is known with a relative uncertainty of 6.6 x 10(-12). It is one of the most accurate fundamental constants to date. A careful analysis shows that knowledge of the electrical size of the proton is nowadays a limitation in this comparison. The aim of muonic hydrogen spectroscopy was to obtain an accurate value of the proton charge radius. However, the value deduced from this experiment contradicts other less accurate determinations. This problem is known as the proton radius puzzle. This new determination of the proton radius may affect the value of the Rydberg constant R-infinity. This constant is related to many fundamental constants; in particular, R-infinity links the two possible ways proposed for the redefinition of the kilogram, the Avogadro constant N-A and the Planck constant h. However, the current relative uncertainty on the experimental determinations of N-A or h is three orders of magnitude larger than the 'possible' shift of the Rydberg constant, which may be shown by the new value of the size of the proton radius determined from muonic hydrogen. The proton radius puzzle will not interfere in the redefinition of the kilogram. After a short introduction to the properties of the proton, we will describe the muonic hydrogen experiment. There is intense theoretical activity as a result of our observation. A brief summary of possible theoretical explanations at the date of writing of the pap...

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Proton charge and magnetic rms radii from the elastic ep scattering data

Cited by 32 publications

References 25 publications

Model independent extraction of the proton magnetic radius from electron scattering

Model independent extraction of the proton magnetic radius from electron scattering

Proton Charge Radius from Electron Scattering

Is the proton radius a player in the redefinition of the International System of Units?

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