RT Journal Article
T1 On the role of isospin violation in the pion–nucleon σ-term
A1 Hoferichter, Martin
A1 Ruiz De Elvira Carrascal, Jacobo
A1 Kubis, Bastian
A1 Meißner, Ulf G.
AB In recent years, a persistent tension between phenomenological and lattice QCD determinations of the pion–nucleon σ-term σπ N has developed. In particular, lattice-QCD calculations have matured to the point that isospin-violating effects need to be included. Here, we point out that the standard conventions adopted in both fields are incompatible, with the data-driven extraction based on the charged-pion mass, but lattice-QCD conventions relying on the mass of the neutral pion to define the isospin limit. The corresponding correction amounts to  σπ N = 3.1(5) MeV when evaluated in chiral perturbation theory with low-energy constants determined from a Roy–Steiner analysis of pion–nucleon scattering as well as σπ N itself. It reduces the tension with lattice QCD, and should be included in the comparison to phenomenological determinations. We also update the extraction from pionic atoms accounting for the latest measurement of the width of pionic hydrogen, σπ N = 59.0(3.5) MeV, and provide the corresponding set of scalar couplings of the nucleon.
PB Elsevier
SN 0370-2693
YR 2023
FD 2023-08-10
LK https://hdl.handle.net/20.500.14352/102076
UL https://hdl.handle.net/20.500.14352/102076
LA eng
NO 2023 Descuento SCOAP
NO Swiss National Science Foundation
NO German Research Foundation
NO Programa Ramón y Cajal
NO Unión Europea. H2020
NO Volkswagen Stiftung
DS Docta Complutense
RD 7 abr 2025