Journal Article

PUBDB-2026-01176

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Absence of strong CP violation

Schierholz, G.DESY*

2025
IOP Publ. Bristol

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Please use a persistent id in citations: doi:10.1088/1361-6471/adc31d

Report No.: DESY-24-038; arXiv:2403.13508

Abstract: Quantum chromodynamics admits a CP violating contribution to the action, the θ term, which is expected to give rise to a nonvanishing electric dipole moment of the neutron. Despite intensive search, no CP violations have been found in the strong interaction. This puzzle is referred to as the strong CP problem. There is evidence that CP is conserved in the confining theory, to the extent that color charges are totally screened for θ > 0 at large distances. It is not immediately obvious that this implies a vanishing dipole moment though. With this Letter I will close the gap. It is shown that in the infinite volume hadron correlation functions decouple from the topological charge, expressed in terms of the zero modes. The reason is that hadrons have a limited range of interaction, while the density of zero modes vanishes with the inverse root of the volume, thus reducing the probability of finding a zero mode in the vicinity to zero. This implies that CP is conserved in the strong interaction.

Keyword(s): CP: violation ; conservation law: CP ; n: electric moment ; charge: topological ; zero mode: density ; charge: color ; strong interaction: CP ; hadron: correlation function ; moment: dipole ; confinement ; quantum chromodynamics ; decoupling ; Theta parameter ; strong CP problem ; lattice QCD ; gauge field topology

Note: 15 pages, 4 figures, clarifications and references added, matches journal version

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Contributing Institute(s):

1. Theorie-Gruppe (T)

Research Program(s):

1. 611 - Fundamental Particles and Forces (POF4-611) (POF4-611)

Experiment(s):

1. No specific instrument

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Database coverage:
; Clarivate Analytics Master Journal List ; Current Contents - Physical, Chemical and Earth Sciences ; Ebsco Academic Search ; Essential Science Indicators ; IF < 5 ; JCR ; National-Konsortium ; SCOPUS ; Science Citation Index Expanded ; Web of Science Core Collection

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