The cosmological moduli problem and naturalness

• Published in: The journal of high energy physics Vol. 2022; no. 2; pp. 138 - 69
• Main Authors: Bae, Kyu Jung, Baer, Howard, Barger, Vernon, Deal, Robert Wiley
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01-02-2022; Springer Nature B.V; Springer Nature; SpringerOpen
• Subjects: Big bang cosmology; Classical and Quantum Gravitation; Constraints; cosmology; Cosmology of Theories BSM; Dark matter; Dilution; Early Universe Particle Physics; Elementary Particles; Gravitinos; Helicity; High energy physics; Models for Dark Matter; Nuclear fusion; Nuclei (nuclear physics); Parameters; Particle decay; Physics; Physics and Astronomy; PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; Quantum Field Theories; Quantum Field Theory; Quantum Physics; Regular Article - Theoretical Physics; Relativity Theory; string phenomenology; String Theory; Supersymmetry; Cosmology of Theories BSM; Supersymmetry; Models for Dark Matter; Early Universe Particle Physics
• ISSN: 1029-8479; 1029-8479
• DOI: 10.1007/JHEP02(2022)138

A
bstract
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
m
ϕ
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
m
ϕ
≳ 2
.
5 × 10
3
TeV with
m
ϕ
<
2
m
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
<
2
m
3
/
2
. In a pedagogical appendix, we present detailed calculations of modulus field two-body decay widths.