The size of the proton

  title={The size of the proton},
  author={Randolf Pohl and Aldo Antognini and François Nez and Fernando Domingues Amaro and Francois Biraben and Jo{\~a}o M. R. Cardoso and Daniel S. Covita and Andreas J Dax and S. K. Dhawan and Luis M P Fernandes and Adolf Giesen and Thomas Graf and Theodor W. H{\"a}nsch and Paul Indelicato and Lucile Julien and Cheng-Yang Kao and Paul E. Knowles and E.-O. Le Bigot and Yi-Wei Liu and Jos{\'e} A. M. Lopes and Livia Ludhova and Cristina Maria Bernardes Monteiro and Françoise Mulhauser and Tobias Nebel and Paul Rabinowitz and Joaquim M.F. dos Santos and Lukas A. Schaller and Karsten Schuhmann and Catherine Schwob and David Taqqu and Jo{\~a}o Veloso and Franz Kottmann},
The proton is the primary building block of the visible Universe, but many of its properties—such as its charge radius and its anomalous magnetic moment—are not well understood. The root-mean-square charge radius, rp, has been determined with an accuracy of 2 per cent (at best) by electron–proton scattering experiments. The present most accurate value of rp (with an uncertainty of 1 per cent) is given by the CODATA compilation of physical constants. This value is based mainly on precision… 
The proton charge radius
Nucleons (protons and neutrons) are the building blocks of atomic nuclei, and are responsible for more than 99% of the visible matter in the universe. Despite decades of efforts in studying its
How Big Is the Proton?
By using laser spectroscopy to study two transitions in muonic hydrogen, researchers determine a value for the root-mean-square charge radius of the proton that differs appreciably from the latest (2010) CODATA recommended value.
Measuring the α-particle charge radius with muonic helium-4 ions
The measurement of two 2S–2P transitions in the muonic helium-4 ion yields a precise determination of the root-mean-square charge radius of the α particle, providing a benchmark for few-nucleon theories, lattice quantum chromodynamics and electron scattering.
The proton radius (puzzle?) and its relatives
The proton radius revisited
The value of the proton size they deduce from their spectra agrees with the value from muonic hydrogen spectroscopy and disagrees with most previous measurements in regular hydrogen—and there were many; the Rydberg constant disagrees with the literature value by more than three standard deviations.
Proton radius measurement using μ p elastic scattering at COMPASS
The determination of the size of the proton, the most abundant hadron in our Universe, has been in the focus of intensive research since more than 60 years [1](see fig. 1 for the history of the
The proton size puzzle: experiment vs theory.
Current status of the proton size puzzle from experimental and theoretical points of view is briefly discussed. The interest to these studies is primarily related to experiments conducted by the
Transverse charge density and the radius of the proton
A puzzling discrepancy exists between the values of the proton charge radius obtained using different experimental techniques: elastic electron-proton scattering and spectroscopy of electronic and
Proton Structure from the Measurement of 2S-2P Transition Frequencies of Muonic Hydrogen
Accurate knowledge of the charge and Zemach radii of the proton is essential, not only for understanding its structure but also as input for tests of bound-state quantum electrodynamics and its predictions for the energy levels of hydrogen.
Measurement of the proton Zemach radius from the hyperfine splitting in muonic hydrogen atom
Muonic hydrogen is a bound state of a proton and a negative muon. Its Bohr radius is 200 times smaller than that of an electronic hydrogen atom. Therefore, a spectroscopy of the muonic hydrogen is


The muonic hydrogen Lamb-shift experiment
The charge radius of the proton, the simplest nucleus, is known from electron-scattering experiments only with a surprisingly low precision of about 2%. The poor knowledge of the proton charge radius
The Lamb Shift Experiment in Muonic Hydrogen
The subject of this thesis is the muonic hydrogen (µp) Lamb shift experiment being performed at the Paul Scherrer Institute, Switzerland. Its goal is to measure the 2S-2P energy difference in µp
Status of the muonic hydrogen Lamb-shift experiment
The Lamb-shift experiment in muonic hydrogen (μ– p) aims to measure the energy difference between the atomic levels to a precision of 30 ppm. This would allow the r.m.s. proton charge radius rp to be
The 2S Lamb shift in muonic hydrogen and the proton rms charge radius
The determination of the proton rms charge radius with an accuracy of 10−3 is the main goal of our experiment, opening the way to check bound‐state QED predictions in hydrogen to a level of 10−7. The
Theory of the Lamb shift in muonic hydrogen.
  • Pachucki
  • Physics
    Physical review. A, Atomic, molecular, and optical physics
  • 1996
A more accurate value for the proton radius is necessary for further improvements of QED tests based on the hydrogen atom and the corrections to the Lamb shift and also to the fine and hyperfine structures that contribute at the 0.01-meV precision level are calculated.
The quantum theory of the electron
The new quantum mechanics, when applied to the problem of the structure of the atom with point-charge electrons, does not give results in agreement with experiment. The discrepancies consist of
High-precision determination of the electric and magnetic form factors of the proton
New precise results of a measurement of the elastic electron-proton scattering cross section performed at the Mainz Microtron MAMI are presented. About 1400 cross sections were measured with negative
Metrology of the hydrogen and deuterium atoms: Determination of the Rydberg constant and Lamb shifts
Abstract:We present a detailed description of several experiments which have been previously reported in several letters: the determination of the 1S Lamb shift in hydrogen by a comparison of the