Couplings between QCD axion and photon from string compactification

Abstract

The QCD axion couplings of various invisible axion models are presented. In particular, the exact global symmetry U(1)${}_{\mathrm{PQ}}$ in the superpotential is possible for the anomalous U(1) from string compactification, broken only by the gauge anomalies at one loop level, and is shown to have the resultant invisible axion coupling to photon, $c_{a\gamma \gamma }\ge \frac{8}{3}-c_{a\gamma \gamma }^{\mathrm{ch}\mathrm{br}}$ where $c_{a\gamma \gamma }^{\mathrm{ch}\mathrm{br}}\simeq 2$. However, this bound is not applicable in approximate U(1)${}_{\mathrm{PQ}}$ models with sufficiently suppressed U(1)${}_{\mathrm{PQ}}$-breaking superpotential terms. We also present a simple method to obtain $c_{a\gamma \gamma }^0$ which is the value obtained above the electroweak scale.

8 pages, 2 figures

References in corpus (3)

• Stringy origin of non-Abelian discrete flavor symmetries
• Flipped SU(5) from Z_{12-I} orbifold with Wilson line
• From the unification scale to the weak scale: A self consistent supersymmetric Dine-Fischler-Srednicki-Zhitnitsky axion model

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• Axion Dark Matter Research with IBS/CAPP
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• The anomalous U(1) global symmetry and flavors from an SU(5) x SU(5)${}^{\prime }$ GUT in $Z_{12-I}$ orbifold compactification
• Naturally realized two dark Z's near the electroweak scale
• Strong CP problem, axions, and cosmological implications of CP violation