Scalar-singlet assisted leptogenesis with CP violation from the vacuum
Abstract In the vanilla type-I seesaw leptogenesis scenario, CP violation required to generate the lepton asymmetries in the heavy Majorana neutrino decays stem from complex Dirac-type Yukawa couplings. In this paper we explore the case in which that CP violation originates from the vacuum expectati...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
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SpringerOpen
2023-01-01
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| Series: | Journal of High Energy Physics |
| Subjects: | |
| Online Access: | https://doi.org/10.1007/JHEP01(2023)010 |
| _version_ | 1797836671635423232 |
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| author | D. M. Barreiros H. B. Câmara R. G. Felipe F. R. Joaquim |
| author_facet | D. M. Barreiros H. B. Câmara R. G. Felipe F. R. Joaquim |
| author_sort | D. M. Barreiros |
| collection | DOAJ |
| description | Abstract In the vanilla type-I seesaw leptogenesis scenario, CP violation required to generate the lepton asymmetries in the heavy Majorana neutrino decays stem from complex Dirac-type Yukawa couplings. In this paper we explore the case in which that CP violation originates from the vacuum expectation value of a complex scalar singlet at a very high scale. This non-trivial CP-violating phase can be successfully communicated to the low-energy neutrino sector via the heavy neutrino portal. The new scalar-singlet degrees of freedom generate new contributions to the CP asymmetries relevant for leptogenesis not only at the one-loop level but also through tree-level three-body decays. These are computed here for an arbitrary number of heavy neutrinos, Higgs doublets and scalar singlets. We also take into account the new decays and scattering processes that enter the unflavoured Boltzmann equations governing the heavy-neutrino particle densities and the (B – L)-asymmetry evolution. Having established the framework of interest, we present a simple model with two RH neutrinos, two Higgs doublets and a complex scalar singlet, supplemented with a Ƶ 8 flavour symmetry. This symmetry minimises the number of free parameters without compromising the possibility of spontaneous CP violation and compatibility with neutrino data. In fact, the only viable Ƶ 8 charge assignment shows a preference for a non-trivial spontaneous CP-violating phase, which in turn leads to a non-vanishing CP asymmetry due to the direct link between high- and low-energy CP violation. An interesting feature of this simple setup is that the usual wave and vertex type-I seesaw contributions to the CP asymmetry vanish due to the Ƶ 8 symmetry. Thus, the observed baryon-to-photon ratio can be explained thanks to the new couplings among the heavy neutrinos and the new scalar degrees of freedom. |
| first_indexed | 2024-04-09T15:12:41Z |
| format | Article |
| id | doaj.art-40b23a0ce1c1493b9ba9545ddd3e7e8a |
| institution | Directory Open Access Journal |
| issn | 1029-8479 |
| language | English |
| last_indexed | 2024-04-09T15:12:41Z |
| publishDate | 2023-01-01 |
| publisher | SpringerOpen |
| record_format | Article |
| series | Journal of High Energy Physics |
| spelling | doaj.art-40b23a0ce1c1493b9ba9545ddd3e7e8a2023-04-30T11:04:45ZengSpringerOpenJournal of High Energy Physics1029-84792023-01-012023114510.1007/JHEP01(2023)010Scalar-singlet assisted leptogenesis with CP violation from the vacuumD. M. Barreiros0H. B. Câmara1R. G. Felipe2F. R. Joaquim3Departamento de Física and CFTP, Instituto Superior Técnico, Universidade de LisboaDepartamento de Física and CFTP, Instituto Superior Técnico, Universidade de LisboaISEL - Instituto Superior de Engenharia de Lisboa, Instituto Politécnico de LisboaDepartamento de Física and CFTP, Instituto Superior Técnico, Universidade de LisboaAbstract In the vanilla type-I seesaw leptogenesis scenario, CP violation required to generate the lepton asymmetries in the heavy Majorana neutrino decays stem from complex Dirac-type Yukawa couplings. In this paper we explore the case in which that CP violation originates from the vacuum expectation value of a complex scalar singlet at a very high scale. This non-trivial CP-violating phase can be successfully communicated to the low-energy neutrino sector via the heavy neutrino portal. The new scalar-singlet degrees of freedom generate new contributions to the CP asymmetries relevant for leptogenesis not only at the one-loop level but also through tree-level three-body decays. These are computed here for an arbitrary number of heavy neutrinos, Higgs doublets and scalar singlets. We also take into account the new decays and scattering processes that enter the unflavoured Boltzmann equations governing the heavy-neutrino particle densities and the (B – L)-asymmetry evolution. Having established the framework of interest, we present a simple model with two RH neutrinos, two Higgs doublets and a complex scalar singlet, supplemented with a Ƶ 8 flavour symmetry. This symmetry minimises the number of free parameters without compromising the possibility of spontaneous CP violation and compatibility with neutrino data. In fact, the only viable Ƶ 8 charge assignment shows a preference for a non-trivial spontaneous CP-violating phase, which in turn leads to a non-vanishing CP asymmetry due to the direct link between high- and low-energy CP violation. An interesting feature of this simple setup is that the usual wave and vertex type-I seesaw contributions to the CP asymmetry vanish due to the Ƶ 8 symmetry. Thus, the observed baryon-to-photon ratio can be explained thanks to the new couplings among the heavy neutrinos and the new scalar degrees of freedom.https://doi.org/10.1007/JHEP01(2023)010Baryo-and LeptogenesisCP ViolationFlavour SymmetriesNeutrino Mixing |
| spellingShingle | D. M. Barreiros H. B. Câmara R. G. Felipe F. R. Joaquim Scalar-singlet assisted leptogenesis with CP violation from the vacuum Journal of High Energy Physics Baryo-and Leptogenesis CP Violation Flavour Symmetries Neutrino Mixing |
| title | Scalar-singlet assisted leptogenesis with CP violation from the vacuum |
| title_full | Scalar-singlet assisted leptogenesis with CP violation from the vacuum |
| title_fullStr | Scalar-singlet assisted leptogenesis with CP violation from the vacuum |
| title_full_unstemmed | Scalar-singlet assisted leptogenesis with CP violation from the vacuum |
| title_short | Scalar-singlet assisted leptogenesis with CP violation from the vacuum |
| title_sort | scalar singlet assisted leptogenesis with cp violation from the vacuum |
| topic | Baryo-and Leptogenesis CP Violation Flavour Symmetries Neutrino Mixing |
| url | https://doi.org/10.1007/JHEP01(2023)010 |
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