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.

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

References in corpus (33)

• The chiral representation of the $\pi N$ scattering amplitude and the pion-nucleon sigma term
• Hadronic Uncertainties in the Elastic Scattering of Supersymmetric Dark Matter
• Pion-nucleon scattering in chiral perturbation theory I: Isospin-symmetric case
• High-precision determination of the pion-nucleon $\sigma$-term from Roy-Steiner equations
• Accurate evaluation of hadronic uncertainties in spin-independent WIMP-nucleon scattering: Disentangling two- and three-flavor effects
• Precision calculation of threshold pi^- d scattering, pi N scattering lengths, and the GMO sum rule
• Universal behavior in the scattering of heavy, weakly interacting dark matter on nuclear targets
• Lattice computation of the nucleon scalar quark contents at the physical point
• Interpreting the recent results on direct search for dark matter particles in terms of relic neutralino
• Improved description of the $\pi N$-scattering phenomenology in covariant baryon chiral perturbation theory
• $\pi$N and strangeness sigma terms at the physical point with chiral fermions
• Nuclear binding near a quantum phase transition
• In-medium chiral perturbation theory beyond the mean-field approximation
• Direct Evaluation of the Quark Content of Nucleons from Lattice QCD at the Physical Point
• Size of the neutralino--nucleon cross--section in the light of a new determination of the pion--nucleon sigma term
• Pion-nucleon scattering in an effective chiral field theory with explicit spin-3/2 fields
• Direct determinations of the nucleon and pion $\sigma$ terms at nearly physical quark masses
• Varying the light quark mass: impact on the nuclear force and Big Bang nucleosynthesis
• Extracting the sigma-term from low-energy pion-nucleon scattering
• In-medium chiral condensate beyond linear density approximation
• Non-perturbative methods for a chiral effective field theory of finite density nuclear systems
• On the analysis of the pion--nucleon $\sigma$--term: The size of the remainder at the Cheng--Dashen point
• The pion-nucleon $\sigma$ term from pionic atoms
• Scalar radius of the pion and zeros in the form factor
• The Nucleon Sigma Term from Threshold Parameters
• The chiral quark condensate and pion decay constant in nuclear matter at next-to-leading order
• Nucleon scalar and tensor charges using lattice QCD simulations at the physical value of the pion mass
• Chiral Lagrangians at finite density
• Nuclear chiral dynamics and phases of QCD
• Chiral Effective Field Theory for Nuclear Matter with long- and short-range Multi-Nucleon Interactions
• Ab-initio calculation of the proton and the neutron's scalar couplings for new physics searches
• Baryon masses and σ-terms in SU(3) BChPT x 1/Nc
• An in-medium chiral power counting for nuclear matter and some applications

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• Reflections on Chiral Symmetry within QCD
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