Related papers: Pion Polarizability 2022 Status Report
Virtual Compton Scattering is studied at the Thomas Jefferson National Accelerator Facility in the energy domain below pion threshold and in the Delta(1232) resonance region. The data analysis is based on the Dispersion Relation (DR)…
We report on a chiral effective field theory calculation of Compton scattering from the proton. Our calculation includes pions, nucleons, and the Delta(1232) as explicit degrees of freedom. It uses the "delta expansion", and so implements…
Interpreting measurements requires a physical theory, but the theory's accuracy may vary across the experimental domain. To optimize experimental design, and so to ensure that the substantial resources necessary for modern experiments are…
Spin polarizabilities provide information on the internal structure of hadrons in the presence of weak external electromagnetic fields, and are actively studied by Compton scattering experiments. They provide finer detail than the regular…
We suggest the most model-independent and simple description of the $\gamma\gamma\rightarrow\pi\pi$ process near threshold in framework of S-matrix approach. The amplitudes contain the pion polarizabilities and rather restricted information…
The process of two pion production in the electron-polarized proton scattering is investigated. In the Weizs\"acker-Williams approximation the differential spectral distributions and the spin-momentum correlations are considered. The spin…
Double-polarization observables in the reaction $\vec{e}p \rightarrow e'\vec{p'}\gamma{}$ have been measured at $Q^2=0.33 (GeV/c)^2$. The experiment was performed at the spectrometer setup of the A1 Collaboration using the 855 MeV polarized…
Below pion threshold virtual Compton scattering off the nucleon gives access to the generalized electromagnetic polarizabilities. Different theoretical results for the generalized polarizabilities have been compared. In particular, the…
We develop a field-theoretic model for the description of proton Compton scattering in which the proton and its excited state, the \Delta+ resonance, are described as part of one multiplet with a single Rarita-Schwinger wavefunction. In…
Using hydrogen and deuterium targets, Compton scattering by the proton and neutron have been studied at the tagged photon beam of the MAMI (Mainz) accelerator using different experimental setups. The theoretical tools for the analysis of…
The forward neutron production in the ep collisions at 300 GeV measured by H1 and ZEUS Collaborations at DESY has been used to estimate the total probability for proton fluctuation into n pi^+ and p pi^0. The probability found is on the…
Deuteron Compton scattering below pion photoproduction threshold is considered in the framework of the non-relativistic diagrammatic approach with the Bonn OBE potential. The complete gauge-invariant set of diagrams is taken into account…
Recent experimental data on tau decays are used to reconstruct the difference in hadronic spectral densities with vector and axial-vector quantum numbers. The saturation of Das-Mathur-Okubo and Weinberg sum rules is studied. Two methods of…
The polarizabilities $\alpha$ (electric), $\beta$ (magnetic) and $\gamma_\pi$ (backward spin) of the nucleon are investigated in terms of degrees of freedom of the nucleon using recent results for the CGLN amplitudes and resonance couplings…
We present fixed-$t$ subtracted dispersion relations for Compton scattering off the nucleon at energies $E_\gamma \leq$ 500 MeV, as a formalism to extract the nucleon polarizabilities with a minimum of model dependence. The subtracted…
We examine elastic Compton scattering off the deuteron for photon energies between 50 MeV and 100 MeV in the framework of chiral effective field theories to next-to-leading order. We compare one theoretical scheme with only pions and…
We formulate a new power-counting scheme for a chiral effective field theory of nucleons, pions, and Deltas. This extends chiral perturbation theory into the Delta-resonance region. We calculate nucleon Compton scattering up to…
Cross sections for \nuc{6}{Li}($\gamma$,$\gamma$)\nuc{6}{Li} have been measured at the High Intensity Gamma-Ray Source (\HIGS) and the sensitivity of these cross sections to the nucleon isoscalar polarizabilities was studied. Data were…
We evaluate the amplitude for $\gamma \gamma \rightarrow \pi^0 \pi^0$ to two loops in chiral perturbation theory. The three new counterterms which enter at this order in the low-energy expansion are estimated with resonance saturation. We…
An experimental setup for studying the Compton scattering of annihilation photons in various (entangled and decoherent) quantum states is presented. Two entangled $\gamma$-quanta with an energy of 511 keV and mutually orthogonal…