The proton radius and its relatives - much ado about nothing?

Meißner, Ulf-G.

doi:10.1088/1742-6596/2586/1/012006

Cited by 4 publications

(2 citation statements)

References 66 publications

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“…These systems are particularly well-suited to accurately determining the RMS (root mean squre) nuclear charge radius (the slope of the Sachs form factor at small momentum transfer, henceforth called 'radius' for brevity), which can be obtained using the spectroscopy of low-lying radiative transitions (mostly 2P − 1S) [1,17,18]. Indeed, historically, the best measurements of absolute radii have been obtained using muonic atom spectroscopy, sometimes leading to unexpected results such as the 'proton radius puzzle' [19][20][21][22][23][24][25].…”

Section: Introductionmentioning

confidence: 99%

Towards Precision Muonic X-ray Measurements of Charge Radii of Light Nuclei

Ohayon,

Abeln,

Bara

et al. 2024

Physics

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We, the QUARTET Collaboration, propose an experiment to measure the nuclear charge radii of light elements with up to 20 times higher accuracy. These are essential both for understanding nuclear physics at low energies, and for experimental and theoretical applications in simple atomic systems. Such comparisons advance the understanding of bound-state quantum electrodynamics and are useful for searching for new physics beyond the Standard Model. The energy levels of muonic atoms are highly susceptible to nuclear structure, especially to the mean square charge radius. The radii of the lightest nuclei (with the atomic number, Z=1,2) have been determined with high accuracy using laser spectroscopy in muonic atoms, while those of medium mass and above were determined using X-ray spectroscopy with semiconductor detectors. In this communication, we present a new experiment, aiming to obtain precision measurements of the radii of light nuclei 3≤Z≤10 using single-photon energy measurements with cryogenic microcalorimeters; a quantum-sensing technology capable of high efficiency with outstanding resolution for low-energy X-rays.

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Section: Introductionmentioning

confidence: 99%

Towards Precision Muonic X-ray Measurements of Charge Radii of Light Nuclei

Ohayon,

Abeln,

Bara

et al. 2024

Physics

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“…We also mention some of the theoretical papers providing the interpretation or reinterpretation of the experimental results, such as, for instance, [10][11][12]. More references on the corresponding experimental and theoretical/interpretational papers can be found, for example, in reviews [13][14][15][16], as well as in the recent presentations at the 25th European Conference on Few-Body Problems in Physics by Antognini [17], Gao [18], and Meissner [19]. Yet the problem has not been resolved yet and the controversy remains as noted, e.g., in reviews [3,14,16].…”

Section: Introductionmentioning

confidence: 99%

Flavor Symmetry of Hydrogen Atoms Potentially Affecting the Proton Radius Deduced from the Electron-Hydrogen Scattering

Oks

2023

Symmetry

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Precise knowledge of such fundamental quantity as the proton charge radius rp is extremely important both for the quantum chromodynamics (for quark-gluon structure) and for atomic physics (for atomic hydrogen spectroscopy). Yet the ambiguity in measuring rp persists for over a dozen of years by now—from the time when in 2010 the muonic hydrogen spectroscopy experiment yielded rp ≈ 0.84 fm in contrast to the form factor experiment by the Mainz group that produced rp ≈ 0.88 fm. Important was that this difference corresponded to about seven standard deviations and therefore was inexplicable. In the intervening dozen of years, more experiments of various kinds were performed in this regard. Nevertheless, the controversy remains, which is why several different types of new experiments are being prepared for measuring rp. In one of our previous papers, we pointed out the factor that was never taken into account by the corresponding research community: the flavor symmetry of electronic hydrogen atoms, whose existence was confirmed by four kinds of atomic or molecular experiments and also evidenced by two kinds of astrophysical observations. Specifically, in that paper there was discussed the possible presence of the second flavor of muonic hydrogen atoms (in the corresponding experimental gas) and its effect on the shift of the ground state of muonic hydrogen atoms due to the proton finite size. In the present paper we analyze the effect of the flavor symmetry of electronic hydrogen atoms on the corresponding elastic scattering cross-section and on the proton charge radius rp deduced from the cross-section. As an example, we use our analytical results for reconciling two distinct values of rp obtained in different elastic scattering experiments: 0.88 fm and 0.84 fm (which is by about 4.5% smaller than 0.88 fm). We show that if the ratio of the second flavor of hydrogen atoms to the usual hydrogen atoms in the experimental gas would be about 0.3, then the extraction of rp from the corresponding cross-section would yield by about 4.5% smaller value of rp compared to its true value. We also derive the corresponding general formulas that can be used for interpreting the future electronic and muonic experiments.

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Sizes of the nucleon

Kaiser,

Weise

2024

Phys. Rev. C

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The proton radius and its relatives - much ado about nothing?

Cited by 4 publications

References 66 publications

Towards Precision Muonic X-ray Measurements of Charge Radii of Light Nuclei

Towards Precision Muonic X-ray Measurements of Charge Radii of Light Nuclei

Flavor Symmetry of Hydrogen Atoms Potentially Affecting the Proton Radius Deduced from the Electron-Hydrogen Scattering

Sizes of the nucleon

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