In the talk, I will review the scattering side of the proton radius puzzle, starting from the original Mainz experiment. I will discuss the results from recent experiments and describe my view of the current situation with regard to the electric and magnetic radii of the proton. The talk will close with an outlook of planned scattering experiments.
In this talk, I will discuss a new measurement of the hydrogen 2S1/2-8D5/2 two-photon transition performed in our group, which produces additional tension within the global dataset of precision hydrogen spectroscopy. In addition, I will present new results where we load a metastable hydrogen beam into a moving optical lattice, which we then decelerate to control the motion of the atoms. This...
I will present the 1S-3S spectroscopy campaign we carried on Deuterium atoms during the winter 2020, using our home-made CW 205 nm laser. I will show for the first time a new systematic effect that we have recently lifted concerning our old atomic beam. I will present the latest analysis results that are still ongoing.
Recent electron-proton elastic scattering data are reanalyzed in terms of discrete derivatives. The pertinence of elastic scattering process is discussed in view of a very precise extraction of the proton radius.
Measurement uncertainty is a key concept of measurement, and while the scientific literature is full of discussion about its meaning and methods of quantitative determination, this literature presents difficulties in characterizing it unambiguously. In particular, measurement uncertainty is often related to various categories of concepts which refer to different ideas: for instance, accuracy...
The CREMA collaboration at the Paul Scherrer Institute is aiming at the measurement of the ground-state hyperfine splitting in muonic hydrogen (μp) with an accuracy of 1 ppm to extract the two-photon- exchange contribution with a relative accuracy of 10−4. From this both the Zemach radius and the inelastic contribution can be obtained.
The principle of the μp HFS experiment is presented...
The main goal of the FAMU experiment is a high precision laser spectroscopy measurement of the ground state of the muonic hydrogen. From the measurement of the muonic hydrogen ground state hyperfine splitting, precise information about the magnetic structure of the proton can be extracted. Even though we are passing through hard times, the preparation work did not stop. In this contribution,...
The muonic atom, a bound state of negative muon and nucleus, has a small orbital radius compared to an ordinary atom. Therefore, muonic atoms are a highly sensitive probe for the interaction between muon and nucleus. While the discrepancy between the charge radii of protons measured by several independent methods has received much attention, knowledge of what happens to the Zemach radius has...
Abstract: Nuclear polarizability effects account for the largest source of the uncertainty in the calculation of
the Lamb-shift in muonic atoms. Combining advanced few-body techniques and effective field
theories developed for studies of nuclear structures and reactions, we are able to provide precise
determinations of these effects and to reliably quantify the associated uncertainties. I...
Effective field theories (EFTs) are exceptionally suited to define and determine the proton radius and its relatives from low energy observables. They not only provide a unified and unambiguous definition of the low energy constants that naturally includes electromagnetic corrections, but they also yield a robust determination of the theoretical uncertainty. In this talk, I will present the...
The energy levels of hydrogen-like atoms can be precisely described by bound-state quantum electrodynamics (QED). The frequency of the narrow 1s-2s transition of atomic hydrogen has
been measured with a relative uncertainty below 10−14. When combined with other spectroscopic measurements of hydrogen and hydrogen-like atoms, the Rydberg constant and the proton charge radius can be determined....
Molecular hydrogen and its ion are the simplest of all molecules and as such are important systems for the development of molecular quantum mechanics. The rovibrational energy level
structure of these one- and two-electron systems can be calculated extremely precisely by quantum-chemical methods which include the determination of relativistic and QED effects.
By comparison with the results...
The determination of the proton charge radius has so far been the domain of low energy experiments. The radius has been extracted from either elastic electron scattering or through line shifts measured by atomic laser spectroscopy.
With the persistent mismatch of experimental results originating from various techniques and experiments, new probes have been advertised. The AMBER experiment at...
The Paul Scherrer Institute MUSE experiment was created a decade ago in response to the Proton Radius Puzzle, the difference observed between muonic hydrogen measurements of the proton radius and the existing electronic measurements. MUSE simultaneously scatters electrons and muons from hydrogen, alternating between beam polarities, to directly compare the cross sections and form factors with...
The MAGIX spectrometer setup at the high-intensity electron
accelerator MESA will be ideally suited to perform precision
measurements of the proton form factors at small four-momentum transfers, reaching below Q^2=0.0001 GeV^2. The key element to the success of this type of experiment, aimed at a precise determination of the proton charge radius, is the absence of a target cell and the very...
The ULQ2 (Ultra Low Q2) experiment at ELPH is aiming at determining the proton charge radius with the electron scattering. The features of the ULQ2 experiment are as follows: absolute cross section measurement with very high accuracy of 0.001 using relative measurement of e+p and e+C, measurement at extremely low momentum transfer region of 0.0003 ≤ Q2 ≤ 0.008 (GeV/c)2 with lowest-ever beam...
The n=2 atomic hydrogen Lamb shift has been measured [1]. An update on this measurement (since it was first announced at the proton radius meeting in Mainz) will be given, including an explanation of the published uncertainty -- which is smaller than that announced in Mainz. Continuing measurements at York of helium fine-structure and of the electron electric dipole moment will also be...
Molecular hydrogen ions (MHI), the simplest molecules, are three-body quantum systems composed of two simple nuclei and one electron. They are of high interest for fundamental physics and metrology because they provide the missing link between the fields of mass and g-factor measurements with Penning traps and spectroscopy of hydrogen-like atoms.
Similar to s-states in the hydrogen atom,...
Recently, considerable progress has been made in the calculation of the energy level structures of the two-electron
systems He and H2. Patkóš, Yerokhin, and Pachucki have performed the first complete calculation of the Lamb shift of the helium 2 3S1 and 2 3PJ triplet states up to the term in a7m [1]. Whereas their theoretical result for the frequency of the 2 3P - 2 3S transition perfectly...
Being purely leptonic, i.e. made of constituents which have (to the best of our knowledge) no internal structure, Muonium (M) is an excellent candidate to probe b-QED. I will present our recent measurement of the n=2 M Lamb Shift of 1047.2(2.5) MHz, which comprises an order of magnitude improvement upon the last determinations and matches with theory within one sigma. This allows us to set...
Recent measurements of the positronium (Ps) 23S1 → 23PJ fine-structure intervals, for νJ (J = 0, 1, 2), are presented. This experiment used slow Ps atoms, which were optically excited to the metastable 23S1 level. This metastable beam then passed through a microwave guide, which produced a radiation field tuned to drive the transition to the short-lived 23PJ levels. These short-lived Ps atoms...
The neutron charge radius can be extracted by determining the slope of Sachs form factor GEn as Q2 -> 0. One can combine global neutron and proton GE data and exploit charge symmetry to perform a flavor dependent decomposition of the nucleon's Dirac form factors and simultaneously extract the proton and neutron charge radii. The resulting proton charge radius using this method is consistent...
I will introduce low-energy electron scattering facilities for nuclear physics that we have constructed in Japan.
1) the ULQ2 facility at Tohoku for the proton radius
Ee = 10 - 60 MeV, \theta_e = 30 - 150 deg..
high-resolution twin spectrometers with 4k-ch silicon strip
detectors.
2) the SCRIT facility in RIKEN/RIBF for short-lived exotic nuclei.
the world’s...
Two photon exchange (TPE) and the larger class of hadronic box diagrams can be a significant radiative correction to lepton scattering and beta decay measurements. Notably, it has been hypothesized that TPE could be responsible for the proton form factor ratio discrepancy. However, these diagrams remain difficult to calculate without large uncertainty and model-dependence, and theoretical...
Nuclear polarizability effects account for the largest source of the uncertainty in the calculation of the Lamb-shift in muonic atoms. Combining advanced few-body techniques and effective field theories developed for studies of nuclear structures and reactions, we are able to provide precise determinations of these effects and to reliably quantify the associated uncertainties. I will review...
Simple systems are an ideal probe to test fundamental physics. At the LaserLaB at the Vrije Universiteit Amsterdam we study several of these systems. One of our goals is to measure the 1S-2S transition in singly-ionized helium with 1 kHz accuracy. Since He+ has twice the nuclear charge of hydrogen, some interesting QED contributions are strongly enhanced and can therefore be tested more...
