Is the magnitude of the Peccei–Quinn scale set by the landscape?

Journal Article · 07 November 2019 · European Physical Journal. C, Particles and Fields

DOI: https://doi.org/10.1140/epjc/s10052-019-7408-x · OSTI ID:1600540

Baer, Howard  ^[1]; Barger, Vernon ^[2]; Sengupta, Dibyashree ^[3]; Serce, Hasan ^[2]; Sinha, Kuver ^[3]; Deal, Robert Wiley ^[3]

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1. Univ. of Oklahoma, Norman, OK (United States); University of Oklahoma
2. Univ. of Wisconsin, Madison, WI (United States)
3. Univ. of Oklahoma, Norman, OK (United States)

Rather general considerations of the string theory landscape imply a mild statistical draw towards large soft SUSY breaking terms tempered by the requirement of proper electroweak symmetry breaking where SUSY contributions to the weak scale are not too far from m_weak~ 100 GeV. Such a picture leads to the prediction that m_h~ 125 GeV while most sparticles are beyond current LHC reach. Here we explore the possibility that the magnitude of the Peccei-Quinn (PQ) scale f_a is also set by string landscape considerations within the framework of a compelling SUSY axion model. First, we examine the case where the PQ symmetry arises as an accidental approximate global symmetry from a more fundamental gravity-safe Z$$R\atop{24}$$$$ symmetry and where the SUSY mu parameter arises from a Kim-Nilles operator. The pull towards large soft terms then also pulls the PQ scale as large as possible. Unless this is tempered by rather severe (unknown) cosmological or anthropic bounds on the density of dark matter, then we would expect a far greater abundance of dark matter than is observed. This conclusion cannot be negated by adopting a tiny axion misalignment angle θ_i because WIMPs are also overproduced at large f_a. Hence, we conclude that setting the PQ scale via anthropics is highly unlikely. Instead, requiring soft SUSY breaking terms of order the gravity-mediation scale m_3/2~ 10_-100 TeV places the mixed axion-neutralino dark matter abundance into the intermediate scale sweet zone where f_a~ 10¹¹-10¹² GeV. We compare our analysis to the more general case of a generic SUSY DFSZ axion model with uniform selection on theta_i but leading to the measured dark matter abundance: this approach leads to a preference for f_a~ 10¹² GeV.

• Research Organization: Univ. of Oklahoma, Norman, OK (United States)
• Sponsoring Organization: USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25)
• Grant/Contract Number: SC0009956
• OSTI ID: 1600540
• Report Number(s): arXiv:1905.00443; arXiv:1905.00443
• Journal Information: European Physical Journal. C, Particles and Fields, Journal Name: European Physical Journal. C, Particles and Fields Journal Issue: 11 Vol. 79; ISSN 1434-6044
• Publisher: SpringerCopyright Statement
• Country of Publication: United States
• Language: English