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String theoretic QCD axion with stabilized saxion and the pattern of supersymmetry breaking

Kiwoon Choi, Kwang Sik Jeong

TL;DR

The work tackles the challenge of embedding the QCD axion in string theory by stabilizing the saxion while keeping the axion flat until QCD effects arise. It introduces a PQ-invariant generalization of KKLT with a sequestered uplifting sector from a warped throat, which yields a mirage pattern of SUSY breaking and preserves flavor and CP through axionic shift symmetries. The authors derive a robust moduli/mass spectrum and universal F-terms, with a near-Planck-scale axion decay constant $v_{\rm PQ}\sim 10^{16}$ GeV, and predict a highly constrained soft-term structure that unifies at the mirage scale. Cosmologically, the framework mitigates the gravitino, moduli, and axion problems by ensuring a heavy saxion that decays before BBN, while keeping the QCD axion as a viable dark matter candidate.

Abstract

String theoretic axion is a prime candidate for the QCD axion solving the strong CP problem. For a successful realization of the QCD axion in string theory, one needs to stabilize moduli including the scalar partner (saxion) of the QCD axion, while keeping the QCD axion unfixed until the low energy QCD instanton effects are turned on. We note that a simple generalization of KKLT moduli stabilization provides such set-up realizing the axion solution to the strong CP problem. Although some details of moduli stabilization are different from the original KKLT scenario, this set-up leads to the mirage mediation pattern of soft SUSY breaking terms as in the KKLT case, preserving flavor and CP as a consequence of approximate scaling and axionic shift symmetries. The set-up also gives an interesting pattern of moduli masses which might avoid the cosmological moduli, gravitino and axion problems.

String theoretic QCD axion with stabilized saxion and the pattern of supersymmetry breaking

TL;DR

The work tackles the challenge of embedding the QCD axion in string theory by stabilizing the saxion while keeping the axion flat until QCD effects arise. It introduces a PQ-invariant generalization of KKLT with a sequestered uplifting sector from a warped throat, which yields a mirage pattern of SUSY breaking and preserves flavor and CP through axionic shift symmetries. The authors derive a robust moduli/mass spectrum and universal F-terms, with a near-Planck-scale axion decay constant GeV, and predict a highly constrained soft-term structure that unifies at the mirage scale. Cosmologically, the framework mitigates the gravitino, moduli, and axion problems by ensuring a heavy saxion that decays before BBN, while keeping the QCD axion as a viable dark matter candidate.

Abstract

String theoretic axion is a prime candidate for the QCD axion solving the strong CP problem. For a successful realization of the QCD axion in string theory, one needs to stabilize moduli including the scalar partner (saxion) of the QCD axion, while keeping the QCD axion unfixed until the low energy QCD instanton effects are turned on. We note that a simple generalization of KKLT moduli stabilization provides such set-up realizing the axion solution to the strong CP problem. Although some details of moduli stabilization are different from the original KKLT scenario, this set-up leads to the mirage mediation pattern of soft SUSY breaking terms as in the KKLT case, preserving flavor and CP as a consequence of approximate scaling and axionic shift symmetries. The set-up also gives an interesting pattern of moduli masses which might avoid the cosmological moduli, gravitino and axion problems.

Paper Structure

This paper contains 5 sections, 65 equations, 2 figures.

Table of Contents

  1. Introduction
  2. Saxion stabilization
  3. Moduli masses, $F$-components and the axion scale
  4. Flavor and CP conserving soft terms
  5. Conclusion

Figures (2)

  • Figure 1: CY space and SUSY-breaking brane sequestered from each other by warped throat. Here the visible sector $D7$ branes are assumed to be wrapping a 4-cycle of CY.
  • Figure 2: Moduli potential along $T_1$ and $T=T_2-T_3$ in unit of $m_{3/2}^2M_{Pl}^2$ for the toy model (2.7). $T_1$ is stabilized by the KKLT superpotential giving $m_{T_1}\sim m_{3/2}\ln(M_{Pl}/m_{3/2})$, while the saxion ${\rm Re}(T)$ is stabilized with $m_s\simeq \sqrt{2}m_{3/2}$ by the sequestered uplifting potential.