1998/09/30 by M. Knecht, Marc Knecht, S. Peris +3 · 1 citation
Physics and Astronomy · #High-Energy Particle Collisions Research #Particle physics theoretical and experimental studies #Quantum Chromodynamics and Particle Interactions #hep-lat #hep-ph
paper · pdf · doi:10.1016/s0370-2693(98)01344-6
published as Phys.Lett.B443:255-263,1998 · 11 pages, LaTeX; typos corrected
openalex publication_date 1998/12/01 · arxiv created 1998/12/07 · arxiv updated 2009/11/30 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28
The pi+ - pi0 mass difference generated by the electroweak interactions of the Standard Model is expressed, to lowest order in the chiral expansion and to leading order in alpha, in terms of an integral involving the same correlation function PiLR(Q2) which governs the well known electromagnetic pi+ - pi0 mass difference. We calculate this contribution within the framework of QCD in the limit of a large number of colours Nc. We show how this calculation, which requires non-trivial contributions from next-to-leading terms in the 1/Nc expansion, provides an excellent theoretical laboratory for studying issues of long- and short-distance matching in calculations of weak matrix elements of four-quark operators. The electroweak pi+ - pi0 mass difference turns out to be a physical observable which is under good analytical control and which should, therefore, be an excellent testground of numerical evaluations in lattice-QCD and of model calculations in general.