A little theory of everything, with heavy neutral leptons
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Springer
Received: February 4, Revised: April 5, Accepted: April 21, Published: May 8,
2020 2020 2020 2020
James Cline,a Matteo Puela and Takashi Tomab a
McGill University, Department of Physics, 3600 University St., Montr´eal, QC H3A2T8 Canada b Institute of Liberal Arts and Science, Kanazawa University, Kakuma-machi, Kanazawa, Ishikawa 920-1192 Japan
E-mail: [email protected], [email protected], [email protected] Abstract: Recently a new model of “Affleck-Dine inflation” was presented, that produces the baryon asymmetry from a complex inflaton carrying baryon number, while being consistent with constraints from the cosmic microwave background. We adapt this model such that the inflaton carries lepton number, and communicates the lepton asymmetry to the standard model baryons via quasi-Dirac heavy neutral leptons (HNLs) and sphalerons. One of these HNLs, with mass . 4.5 GeV, can be (partially) asymmetric dark matter (DM), whose asymmetry is determined by that of the baryons. Its stability is directly related to the vanishing of the lightest neutrino mass. Neutrino masses are generated by integrating out heavy sterile neutrinos whose mass is above the inflation scale. The model provides an economical origin for all of the major ingredients missing from the standard model: inflation, baryogenesis, neutrino masses, and dark matter. The HNLs can be probed in ¯ oscillations. A light singlet fixed-target experiments like SHiP, possibly manifesting N -N scalar, needed for depleting the DM symmetric component, can be discovered in beam dump experiments and searches for rare decays, possibly explaining anomalous events recently observed by the KOTO collaboration. The DM HNL is strongly constrained by direct searches, and could have a cosmologically interesting self-interaction cross section. Keywords: Cosmology of Theories beyond the SM, Neutrino Physics ArXiv ePrint: 2001.11505
c The Authors. Open Access, Article funded by SCOAP3 .
https://doi.org/10.1007/JHEP05(2020)039
JHEP05(2020)039
A little theory of everything, with heavy neutral leptons
Contents 1
2 Model
3
3 Nonstandard leptogenesis and DM relic density 3.1 Sharing and preserving the asymmetry 3.2 DM asymmetric abundance and maximum mass 3.3 Dark matter annihilation and relic density ¯ 0 → ss annihilation 3.3.1 N 0 N ¯ 0 → SM annihilation 3.3.2 N 0 N
4 5 6 7 8 9
4 Neutrino properties and HNL constraints 4.1 Explicit ην and HNL mixings 4.1.1 Unitarity constraints for ms < MN case 4.1.2 Laboratory constraints for ms > MN case ¯ oscillations 4.2 N -N 4.3 Weak HNL decays 4.4 Entropy and energy injection by late N decays 4.5 Lepton flavor violation bounds
10 10 11 13 15 15 16 17
5 Constraints on the singlet
18
6 DM 6.1 6.2 6.3
19 19 21 23
direct/indirect detection and self-interactions DM-nucleon scattering DM indirect detection DM self-interactions
7 Naturalness
24
8 Conclusions
25
A Decay rate for Ni → ν`+ `−
27
1
Introduction
The standard model (SM) of particle physics is noted for being incomplete in numerous
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