The cosmological moduli problem and naturalness

Journal Article · 16 February 2022 · Journal of High Energy Physics (Online)

DOI: https://doi.org/10.1007/jhep02(2022)138 · OSTI ID:1865420

Bae, Kyu Jung ^[1]; Baer, Howard A.  ^[2]; Barger, Vernon ^[3]; Deal, Robert Wiley ^[2]

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1. Kyungpook National Univ., Daegu (Korea, Republic of); University of Oklahoma
2. Univ. of Oklahoma, Norman, OK (United States); Univ. of Wisconsin, Madison, WI (United States)
3. Univ. of Wisconsin, Madison, WI (United States)

Nowadays, the cosmological moduli problem (CMP) comes in three parts: 1. potential violation of Big-Bang nucleosynthesis (BBN) constraints from late decaying moduli fields, 2. the moduli-induced gravitino problem wherein gravitinos are overproduced and their decays violate BBN or dark matter overproduction bounds and 3. the moduli-induced lightest SUSY particle (LSP) overproduction problem. Also, the CMP may be regarded as either a problem or else a solution to scenarios with dark matter over- or under-production. We examine the cosmological moduli problem and its connection to electroweak naturalness. We calculate the various two-body decay widths of a light modulus field into MSSM particles and gravitinos within general supersymmetric models. We include both phase space and mixing effects. We examine cases without and with helicity suppression of modulus decays to gravitinos (cases 1 & 2) and/or gauginos (cases A & B). For case B1, we evaluate regions of gravitino mass m_3/2 vs. modulus mass mΦ parameter space constrained by BBN, by overproduction of gravitinos and by overproduction of neutralino dark matter, along with connections to naturalness. For this case, essentially all of parameter space is excluded unless mΦ ≳ 2.5 × 10³ TeV with mΦ< 2m_3/2 For a potentially most propitious case B2 with Φ decay to Higgs and matter turned off, then modulus branching fractions to SUSY and to gravitinos become highly suppressed at large m_Φ. But since the modulus number density increases faster than the branching fractions decrease, there is still gross overproduction of neutralino dark matter. We also show that in this scenario the thermally produced gravitino problem is fixed by huge entropy dilution, but non-thermal gravitino production from moduli decay remains a huge problem unless it is kinematically suppressed with m_Φ < 2m_3/2 . In a pedagogical appendix, we present detailed calculations of modulus field two-body decay widths.

• Research Organization: Univ. of Oklahoma, Norman, OK (United States)
• Sponsoring Organization: USDOE Office of Science (SC), High Energy Physics (HEP)
• Grant/Contract Number: SC0009956
• OSTI ID: 1865420
• Journal Information: Journal of High Energy Physics (Online), Journal Name: Journal of High Energy Physics (Online) Journal Issue: 2 Vol. 2022; ISSN 1029-8479
• Publisher: Springer NatureCopyright Statement
• Country of Publication: United States
• Language: English