The proton charge radius extracted from the initial-state radiation experiment at MAMI

We report on a comprehensive reinterpretation of the existing cross-section data for elastic electron-proton scattering obtained by the initial-state radiation technique, resulting in a significantly improved accuracy of the extracted proton charge radius. By refining the external energy corrections we have achieved an outstanding description of the radiative tail, essential for a detailed investigation of the proton finite-size effects on the measured cross sections. This development, together with a novel framework for determining the radius, based on a regression analysis of the cross sections employing a polynomial model for the form factor, led us to a new value for the charge radius, which is $$(0.878 \pm 0.011_\mathrm {stat.}\pm 0.031_\mathrm {sys.}\pm 0.002_\mathrm {mod.})\,\mathrm {fm}$$ ( 0.878 ± 0 . 011 stat . ± 0 . 031 sys . ± 0 . 002 mod . ) fm

Two-photon frequency comb spectroscopy of atomic hydrogen

We have performed two-photon ultraviolet direct frequency comb spectroscopy on the 1S-3S transition in atomic hydrogen to illuminate the so-called proton radius puzzle and to demonstrate the potential of this method. The proton radius puzzle is a significant discrepancy between data obtained with muonic hydrogen and regular atomic hydrogen that could not be explained within the framework of quantum electrodynamics. By combining our result [f1S-3S = 2,922,743,278,665.79(72) kilohertz] with a previous measurement of the 1S-2S transition frequency, we obtained new values for the Rydberg constant [R∞ = 10,973,731.568226(38) per meter] and the proton charge radius [rp = 0.8482(38) femtometers]. This result favors the muonic value over the world-average data as presented by the most recent published CODATA 2014 adjustment.

Theoretical Determination of the Mass Radii of the Nucleons and Heavier Subatomic Particles

Background: The literature contains numerous values of nucleon charge radii with greater interest in proton. The mean square negative radii are reported for the neutron, the scientific relevance notwithstanding. Only in very few instances was the mass radius of the nucleon investigated. Methods: Theoretical and computational methods. Objectives: The objectives of this research are to derive, based mainly on classical model, the equation of the radii of nucleons and other subatomic particles heavier than the nucleons and determine by calculation based on the equation the radii of such particles, and elucidate why results may be different from literature values. Results and Discussion: The results showed expectedly that the mass radii of nucleons and heavier subatomic particles are longer than what seemed to be the preferred proton charge radius. The lengths of the calculated radii increase with increase in rest mass of the subatomic particles whose mass must be ³ the mass of any nucleon Conclusion: The equation of the mass radius of any nucleon and heavier subatomic particles was derived. Expectedly, the radii differ on the basis of differences in masses of the particles. The difference in mass radii as calculated in this research and reported charge radii in the literature may be due to electron capture leading to greater number of elastic collision with resulting neutrons. Two particles of widely different mass possessing different charge must interact attractively or repulsively if they possess similar charges. Otherwise the deflection of beta–rays and similar particles in an electromagnetic field would be impossible.