The Kinoshita-Lee-Nauenberg theorem or KLN theorem states that perturbatively the Standard model as a whole is infrared (IR) finite. That is, the infrared divergences coming from loop integrals are canceled by IR divergences coming from phase space integrals. It was introduced independently by Kinoshita (1962) and Lee and Nauenberg (1964).
An analogous result for quantum electrodynamics alone is known as Bloch-Nordsieck cancellation.
- Kinoshita, Toichiro (1962), Mass Singularities of Feynman Amplitudes, Journal of Mathematical Physics 3: 650, Bibcode:1962JMP.....3..650K, doi:10.1063/1.1724268, ISSN 0022-2488
- Lee, Tsung-Dao; Nauenberg, Michael (1964), Degenerate Systems and Mass Singularities, Physical Review D 133: B1549, Bibcode:1964PhRv..133.1549L, doi:10.1103/PhysRev.133.B1549
- Taizo Muta, Foundations of Quantum Chromodynamics: An Introduction to Perturbative Methods in Gauge Theories, World Scientific Publishing Company; 3 edition (September 30, 2009)