Abstract
The gauged Peccei-Quinn (PQ) mechanism provides a simple prescription to embed the global PQ symmetry into a gauged U(1) symmetry. As it originates from the gauged PQ symmetry, the global PQ symmetry can be protected from explicit breaking by quantum gravitational effects once appropriate charge assignment is given. In this paper, we identify the gauged PQ symmetry with the B − L symmetry, which is obviously attractive as the B − L gauge symmetry is the most authentic extension of the Standard Model. As we will show, a natural B − L charge assignment can be found in a model motivated by the seesaw mechanism in the SU(5) Grand Unified Theory. As a notable feature of this model, it does not require extra SU(5) singlet matter fields other than the right-handed neutrinos to cancel the self and the gravitational anomalies.
Highlights
In this paper, we discuss whether the B −L symmetry can play a role of the gauged PQ symmetry
We identify the gauged PQ symmetry with the B − L symmetry, which is obviously attractive as the B − L gauge symmetry is the most authentic extension of the Standard Model
We find that the gauged PQ mechanism based on the fiveness can solve the strong CP problem while satisfying the astrophysical constraint from the observation of supernova 1987A, FA GeV [39], and the condition for successful thermal leptogenesis, MN = yN φ GeV [31,32,33]
Summary
To see the properties of the accidental global PQ symmetry, let us decompose the axion from the would-be Goldstone boson of fiveness Both of them originate from the phase components of φ and φ ; φ=. Which reproduces the axial anomaly of eq (2.14) by the shift of the axion in eq (3.12) Through this term, the axion obtains a mass from the anomalous coupling below the QCD scale, with which the QCD vacuum angle is erased. Such a small shift should be consistent with the current experimental upper limit on the θ angle, θ 10−10 [38]. As B − L is an accidental symmetry of the SM except for the neutrino masses, the current couplings to the axion proportional to the fiveness can be absorbed by the B − L rotation and U(1)Y rotation. It seems very difficult to test the direct couplings between the axion and the neutrinos in laboratory experiments
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