Brief history of the pion–nucleon sigma term
University of Alcalá, Nuclear and Particle Physics Group, Department of Physics and Mathematics, 28805, Alcalá de Henares, Madrid, Spain
Accepted: 10 May 2021
Published online: 5 June 2021
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 ( MeV) to larger ones ( MeV) until today, where this controversy still persist.
© The Author(s), under exclusive licence to EDP Sciences, Springer-Verlag GmbH Germany, part of Springer Nature 2021