Brief history of the pion-nucleon sigma term

Abstract

The pion-nucleon sigma term is a quantity involved in many important aspects of particle and nuclear physics. In this review I show its origin and how it is connected to important questions as the origin of mass of the ordinary matter, studies of dark matter detection and nucleosynthesis. I mention the most common methods used to obtain the sigma term, and comment on the extracted values. As it is shown, the accepted value of the sigma term has been moving from relatively low ($\sim 40$ MeV) to larger ones ($\sim 60$ MeV) until today, where this controversy still persist.

Invited review for European Physical Journal Special Topics (REVTeX version). 34 pages, 5 figures. Accepted for publication on 10 May 2021

References in corpus (8)

• Hadronic Uncertainties in the Elastic Scattering of Supersymmetric Dark Matter
• Interpreting the recent results on direct search for dark matter particles in terms of relic neutralino
• Extracting the sigma-term from low-energy pion-nucleon scattering
• In-medium chiral condensate beyond linear density approximation
• Scalar radius of the pion and zeros in the form factor
• The pion-nucleon $\sigma$ term from pionic atoms
• The chiral quark condensate and pion decay constant in nuclear matter at next-to-leading order
• Ab-initio calculation of the proton and the neutron's scalar couplings for new physics searches

Cited by in corpus (6)

• Glue in hadrons at medium resolution and the QCD instanton vacuum
• Pi in the Sky: Neutron Stars with Exceptionally Light QCD Axions
• Chiral Perturbation Theory Reflections on Effective Theories of the Standard Model
• Octet and decuplet baryon $\sigma$-terms and mass decompositions
• Reflections on Chiral Symmetry within QCD
• Quark model of nucleon based on an analogy with polaron