Point-Particle Effective Field Theory III: Relativistic Fermions and the Dirac Equation
arXiv:1706.01063 · doi:10.1007/JHEP09(2017)007
Abstract
We formulate point-particle effective field theory (PPEFT) for relativistic spin-half fermions interacting with a massive, charged finite-sized source using a first-quantized effective field theory for the heavy compact object and a second-quantized language for the lighter fermion with which it interacts. This description shows how to determine the near-source boundary condition for the Dirac field in terms of the relevant physical properties of the source, and reduces to the standard choices in the limit of a point source. Using a first-quantized effective description is appropriate when the compact object is sufficiently heavy, and is simpler than (though equivalent to) the effective theory that treats the compact source in a second-quantized way. As an application we use the PPEFT to parameterize the leading energy shift for the bound energy levels due to finite-sized source effects in a model-independent way, allowing these effects to be fit in precision measurements. Besides capturing finite-source-size effects, the PPEFT treatment also efficiently captures how other short-distance source interactions can shift bound-state energy levels, such as due to vacuum polarization (through the Uehling potential) or strong interactions for Coulomb bound states of hadrons, or any hypothetical new short-range forces sourced by nuclei.
29 pages plus appendices, 3 figures
References in corpus (13)
- Introduction to Effective Field Theory
- The Proton Radius Puzzle
- Model independent extraction of the proton charge radius from electron scattering
- Muonic hydrogen and MeV forces
- The RMS Charge Radius of the Proton and Zemach Moments
- New Parity-Violating Muonic Forces
- Proton size anomaly
- Model independent extraction of the proton magnetic radius from electron scattering
- Evidence For The Production Of Slow Antiprotonic Hydrogen In Vacuum
- The Hierarchy Problem and the Self-Localized Higgs
- Model independent determination of the muonic hydrogen Lamb shift and proton radius
- Breakdown of the expansion of finite-size corrections to the hydrogen Lamb shift in moments of charge distribution
- Robin boundary conditions are generic in quantum mechanics