580 California St., Suite 400
San Francisco, CA, 94104
Key research themes
1. How can proton charge radius be precisely extracted from electron-proton scattering experiments to address the proton radius puzzle?
This research theme investigates the methodology and precision extraction of the proton charge radius (r_p) using elastic electron-proton scattering, in light of discrepancies known as the proton radius puzzle, where different experimental techniques (electron scattering, muonic hydrogen spectroscopy) report conflicting radius values. Accurate extraction is crucial for fundamental constants, quantum electrodynamics tests, and hadronic physics, and requires innovative experimental design and careful data analysis accounting for low momentum transfer limits and systematics.
Key finding: The PRad experiment introduced a magnetic-spectrometer-free technique and a windowless hydrogen gas target to reduce systematic uncertainties, enabling measurements at ultra-low Q^2 (~2.1 × 10^(-4) (GeV/c)^2) —an order of... Read more
Key finding: This work critically analyzed various parameterizations used in fitting electron-proton scattering form factor data, highlighting the significant model dependence in extrapolating G_E(q^2) to q^2 = 0. By incorporating... Read more
Key finding: The PSI MUSE experiment presents a design to measure simultaneously muon-proton and electron-proton elastic scattering cross sections with sub-percent precision at low momentum transfers (<0.1 GeV^2), enabling direct lepton... Read more
Key finding: This study provided an in-depth analysis of higher-order quantum electrodynamics radiative corrections—especially vacuum polarization and multiple photon emissions—in electron-proton scattering experiments with precision... Read more
2. How do proton scattering theoretical models incorporate nuclear structure effects to accurately predict cross sections and spin observables?
This theme explores the use of advanced nuclear structure models, especially Skyrme-Hartree-Fock (SHF) calculations, combined with microscopic nucleon-nucleon interactions to build realistic optical potentials for proton elastic scattering. The goal is to understand how proton and neutron density distributions, including those affected by shell-model occupation and exotic neutron-rich isotopes, influence scattering observables. Reliable structure-dependent potentials allow parameter-free predictions crucial for probing nuclear densities, exotic structures (skins, halos), and validating model assumptions.
Key finding: By folding proton and neutron densities derived from Skyrme-Hartree-Fock calculations with realistic nucleon-nucleon g-matrix interactions, the authors generated non-local optical potentials that predicted elastic proton... Read more
Key finding: Using a relativistic optical potential with Lorentz scalar and vector Gaussian potentials, this work described proton elastic scattering differential cross sections and polarizations on 4He over intermediate energies,... Read more
3. How does polarization transfer in proton scattering reflect nuclear medium and proton initial momentum effects?
This theme addresses the interpretation of polarization transfer measurements in elastic and quasi-elastic proton scattering to probe modifications of the proton’s internal structure within the nuclear medium. Emphasis is placed on accounting for the Fermi motion of bound nucleons by introducing moving-proton kinematics rather than assuming protons at rest. Correcting for proton initial momentum effects improves comparison with free proton scattering, isolating genuine medium modifications and nuclear effects. Such insights help disentangle complex nuclear reaction mechanisms (FSI, MEC, IC) from intrinsic proton property changes.
Key finding: The authors derived expressions for polarization-transfer components for protons initially in motion (moving-proton kinematics) and compared these theoretically to MAMI 2H data. They found that accounting for the initial... Read more