The Strong CP problem and axions

By Glenn Wouda. 2006

446 citations recorded by the source corpus.

I describe how the QCD vacuum structure, necessary to resolve the U(1)_A problem, predicts the presence of a PabbrevPparity transformation, TabbrevTtime reversal transformation, and CPabbrevCPcharge conjugation transformation followed by party transformation 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 other possible 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.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/788af220d520fe80473e0267f39d8a116487635d

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

In Nuclear and High Energy Physics

Citations in the corpus

Search for New Physics with Atoms and Molecules (2017, unknown): “In addition, there is the possibility in quantum chromodynamics (QCD) of an irreducible CPV interaction (see, for example, the reviews by Peccei (2008), Kim and Carosi (2010), and Sikivie 2012), described by the Lagrangian density Lθ = −θ̄QCD(αs/8π)( µνκλ/2)GaµνGaκλ.”
Axion Cosmology (2015, background): “Many such reviews and published lecture notes focus on the QCD axion and its role in solving the strong-CP problem [6, 7], as well as its important cosmological role [8].”
An improved limit on the axion–photon coupling from the CAST experiment (2007, background): “The Peccei–Quinn (PQ) mechanism [1]–[3] remains perhaps the most compelling explanation of the CP problem of strong interactions.”
Axions (2003, unknown): “For more information about the topological properties of instantons and the QCD vacuum in the context of axions, one can see [2] and references therein.”
Rare $B$ Decays as Tests of the Standard Model (2016, background): “Another class of models invokes the axial-vector portal in theories of dark matter that seek to address the cosmic ray anomalies [292–297], and to explain the suppression of CP violation in strong interactions [298].”
Probing eV-scale axions with CAST (2008, background): “eter plane spanned by g aγ and m a. The main motivation, however, is to search for QCD axions that appear as a consequence of the Peccei-Quinn mechanism to solve the CP problem of strong interactions [14]. For these particles we have g aγ = α 2π 1 f a E N − 2 3 4+z 1+z , m a = z1/2 1+z f πm π f a ”