Chiral Perturbation Theory and Baryon Properties

Theoretical as well as experimental progress has been made in the last decade in describing the properties of baryons. In this review I will mostly report on the theoretical issues. Two non-perturbative methods are privileged frameworks for studying these properties in the low energy domain: chiral perturbation theory, the effective field theory of the Standard Model at energies below 1 GeV and lattice QCD. I will mainly concentrate here on the first one but I will also discuss the complementarity of the two methods. Chiral extrapolations for lattice simulations of some nucleon properties will be investigated. I will then concentrate on processes involving at most two nucleons, describing for example pion-nucleon and pion-deuteron scattering, pion photo- and electroproduction off the nucleon and the deuteron and doubly virtual Compton scattering. Three flavor calculations will also be reviewed.

The symmetry energy describes how the energy of nuclear matter rises as one goes away from equal numbers of neutrons and protons. This is very important to describe neutron rich matter in astrophysics. This article reviews our knowledge of the symmetry energy from theoretical calculations, nuclear structure measurements, heavy-ion collisions, and astronomical observations. We then present a roadmap to make progress in areas of relevance to the symmetry energy that promotes collaboration between the astrophysics and the nuclear physics communities.

/pdf/a-way-forward-in-the-study-of-the-symmetry-energy-experiment-rqiu5vqddt.pdf

A way forward in the study of the symmetry energy: experiment, theory, and observation

Elastic electromagnetic nucleon form factors have long provided vital information about the structure and composition of these most basic elements of nuclear physics. The form factors are a measurable and physical manifestation of the nature of the nucleons' constituents and the dynamics that binds them together. Accurate form factor data obtained in recent years using modern experimental facilities has spurred a significant reevaluation of the nucleon and pictures of its structure; e.g., the role of quark orbital angular momentum, the scale at which perturbative QCD effects should become evident, the strangeness content, and meson-cloud effects. We provide a succinct survey of the experimental studies and theoretical interpretation of nucleon electromagnetic form factors.

http://iopscience.iop.org/article/10.1088/0954-3899/34/7/S03/pdf

Nucleon electromagnetic form factors

The symmetry energy describes how the energy of nuclear matter rises as one goes away from equal numbers of neutrons and protons. This is very important to describe neutron rich matter in astrophysics. This article reviews our knowledge of the symmetry energy from theoretical calculations, nuclear structure measurements, heavy ion collisions, and astronomical observations. We then present a roadmap to make progress in areas of relevance to the symmetry energy that promotes collaboration between the astrophysics and the nuclear physics communities.

/pdf/a-way-forward-in-the-study-of-the-symmetry-energy-experiment-3gx8miw5j7.pdf

We have measured parity-violating asymmetries in elastic electron-proton scattering over the range of momentum transfers 0.12 ≤ Q^2 ≤ =1.0 GeV^2. These asymmetries, arising from interference of the electromagnetic and neutral weak interactions, are sensitive to strange-quark contributions to the currents of the proton. The measurements were made at Jefferson Laboratory using a toroidal spectrometer to detect the recoiling protons from a liquid hydrogen target. The results indicate nonzero, Q^2 dependent, strange-quark
contributions and provide new information beyond that obtained in previous experiments.

/pdf/strange-quark-contributions-to-parity-violating-asymmetries-2o4oqy4xpz.pdf

P. Bosted

Papers

Strange-quark contributions to parity-violating asymmetries in the forward G0 electron-proton scattering experiment