Color unified dynamical axion

We consider an enlarged color sector which solves the strong CP problem via new massless fermions. The spontaneous breaking of a unified color group into QCD and another confining group provides a source of naturally large axion mass m a due to small size instantons. This extra source of axion mass...

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Bibliographic Details
Published in:The European physical journal. C, Particles and fields Particles and fields, 2018-11, Vol.78 (11), p.1-21, Article 972
Main Authors: Gaillard, M. K., Gavela, M. B., Houtz, R., Quilez, P., del Rey, R.
Format: Article
Language:English
Subjects:
Astronomy
Astrophysics and Cosmology
Color
Confining
Couplings
Elementary Particles
Fermions
Hadrons
Heavy Ions
Instantons
Measurement Science and Instrumentation
Nuclear Energy
Nuclear Physics
Physics
Physics and Astronomy
PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
Quantum Field Theories
Quantum Field Theory
Regular Article - Theoretical Physics
String Theory
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Summary:We consider an enlarged color sector which solves the strong CP problem via new massless fermions. The spontaneous breaking of a unified color group into QCD and another confining group provides a source of naturally large axion mass m a due to small size instantons. This extra source of axion mass respects automatically the alignment of the vacuum, ensuring a low-energy CP-conserving vacuum. The mechanism does not appeal to a Z 2 “mirror” copy of the SM, nor does it require any fine-tuning of the axion-related couplings at the unification scale. There is no very light axion and uncharacteristically the lighter spectrum contains instead sterile fermions. The axion scale f a can be naturally brought down to a few TeV, with an exotic spectrum of colored pseudoscalars lighter than this scale, observable at colliders exclusively via strong interactions. The { m a , f a } parameter space which allows a solution of the strong CP problem is thus enlarged well beyond that of invisible axion models.
ISSN:1434-6044
1434-6052
DOI:10.1140/epjc/s10052-018-6396-6