Split SIMPs with decays
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Springer
Received: July 20, Revised: August 30, Accepted: September 7, Published: October 8,
2020 2020 2020 2020
Split SIMPs with decays
a
Theoretical Physics Department, CERN, Esplanade des Particules 1, 1211 Gen`eve 23, Switzerland b D´epartement de Physique Th´eorique and Center for Astroparticle Physics (CAP), Universit´e de Gen`eve, Quai Ernest-Ansermet 24, 1211 Gen`eve 4, Switzerland
E-mail: [email protected], [email protected], [email protected] Abstract: We discuss a minimal realization of the strongly interacting massive particle (SIMP) framework. The model includes a dark copy of QCD with three colors and three light flavors. A massive dark photon, kinetically mixed with the Standard Model hypercharge, maintains kinetic equilibrium between the dark and visible sectors. One of the dark mesons is necessarily unstable but long-lived, with potential impact on CMB observables. We show that an approximate “isospin” symmetry acting on the down-type quarks is an essential ingredient of the model. This symmetry stabilizes the dark matter and allows to split sufficiently the masses of the other states to suppress strongly their relic abundances. We discuss for the first time the SIMP cosmology with sizable mass splittings between all meson multiplets. We demonstrate that the SIMP mechanism remains efficient in setting the dark matter relic density, while CMB constraints on unstable relics can be robustly avoided. We also consider the phenomenological consequences of isospin breaking, including dark matter decay. Cosmological, astrophysical, and terrestrial probes are combined into a global picture of the parameter space. In addition, we outline an ultraviolet completion in the context of neutral naturalness, where confinement at the GeV scale is generic. We emphasize the general applicability of several novel features of the SIMP mechanism that we discuss here. Keywords: Beyond Standard Model, Cosmology of Theories beyond the SM ArXiv ePrint: 2006.15148
c The Authors. Open Access, Article funded by SCOAP3 .
https://doi.org/10.1007/JHEP10(2020)049
JHEP10(2020)049
Andrey Katz,a,b Ennio Salvionia and Bibhushan Shakyaa
Contents 1 Introduction
1
2 Effective theory for the hidden mesons 2.1 Mass spectrum
3 5
3 Ultraviolet completions in neutral naturalness
8 10 10 12
5 Cosmological history 5.1 Freezeout and relic abundances 5.2 Consequences of π0 -K0 mass splitting 5.3 Larger mass splittings 5.4 Thermalization of hidden and SM sectors 5.5 Suppressed semi-annihilation to dark photon and annihilation to SM
13 13 16 17 18 19
6 Constraints and signatures 6.1 η decays 6.2 Dark matter decays 6.3 Dark matter self-interactions 6.4 Dark photon searches at laboratory experiments 6.5 Dark matter direct detection and annihilation to SM 6.6 Parameter space overview
20 20 21 23 24 26 26
7 Summary and outlook
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A Boltzmann equations
30
1
Introduction
In recent years, the strongly interacting massive particle (SIMP) framework [1] has emerged as an attractive possibility for thermal dark matter,
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