The Strong CP Problem and Axions

2006/07/24 by R. D. Peccei · 1 voice · 12 citations
#hep-ph

paper · pdf · doi:10.1007/978-3-540-73518-2_1

Abstract

I describe how the QCD vacuum structure, necessary to resolve the U(1)_A problem, predicts the presence of a P, T and CP violating term proportional to the vacuum angle θ. To agree with experimental bounds, however, this parameter must be very small (θ ≤ 10^-9). After briefly discussing some possible other solutions to this, so-called, strong CP problem, I concentrate on the chiral solution proposed by Peccei and Quinn which has associated with it a light pseudoscalar particle, the axion. I discuss in detail the properties and dynamics of axions, focusing particularly on invisible axion models where axions are very light, very weakly coupled and very long-lived. Astrophysical and cosmological bounds on invisible axions are also briefly touched upon.

Cited by

• A multi-axion model of inflation and dark matter
• Search for exotic Higgs boson decays H → 𝒜𝒜 with 𝒜 → γγ in events with a semi-merged topology in proton-proton collisions at √(s)=13 TeV
• Quantum Information Meets High-Energy Physics: Probing Neutrinos and Beyond
• Refined Low-Energy Supernova Constraints on Lepton Flavor Violating Axions
• The Good Qualities of the Weak Axion
• Constraints on WIMP-like dark matter scattering on electrons with COSINE-100
• Limits on the Axion-Photon Coupling from Chandrayaan-2
• Probing Long-Lived Photophobic Axion-Like Particles via Prompt Leptons and Mono-γ at FCC-ee and CEPC
• Hiding in Plain Sight, the electroweak η_W
• Constraints on axionlike particles from 16.5 years of Fermi-LAT data and prospects for VLAST
• Bayesian frequency estimation at the fundamental quantum limit
• Smoking gun signature from axion and the constraints with radio telescopes

Discussions

• I am reading this https://arxiv.org/abs/hep-ph/0607268 paper, the Strong CP Problem and Axions by R. D. Peccei. Here they say that $$\bigg = - \frac{\xi}{f_a} \frac{g_s^2}{32\pi^2}\left \bigg|_{ = \th [stackexchange, 5 points]

Related

• CP-Conservation in QCD and why only "invisible" Axions work
• QCD axion and quintessential axion
• CP-Violating Axions: A Theory Review
• Solving the Strong CP Problem with High-Colour Quarks and Composite Axion
• Absence of CP Violation in the Strong Interaction: Vacuum thwarts Axion