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Author |
Donini, A.; Hernandez, P.; Lopez-Pavon, J.; Maltoni, M. |
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Title |
Minimal models with light sterile neutrinos |
Type |
Journal Article |
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Year |
2011 |
Publication |
Journal of High Energy Physics |
Abbreviated Journal |
J. High Energy Phys. |
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Volume |
07 |
Issue |
7 |
Pages |
105 |
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Abstract |
We study the constraints imposed by neutrino oscillation experiments on the minimal extensions of the Standard Model (SM) with n(R) gauge singlet fermions (“right-handed neutrinos”), that can account for neutrino masses. We consider the most general coupling of the new fields to the SM fields, in particular those that break lepton number and we do not assume any a priori hierarchy in the mass parameters. We proceed to analyze these models starting from the lowest level of complexity, defined by the number of extra fermionic degrees of freedom. The simplest choice that has enough free parameters in principle (i.e. two mass differences and two angles) to explain the confirmed solar and atmospheric oscillations corresponds to n(R) = 1. This minimal choice is shown to be excluded by data. The next-to-minimal choice corresponds to n(R) = 2. We perform a systematic study of the full parameter space in the limit of degenerate Majorana masses by requiring that at least two neutrino mass differences correspond to those established by solar and atmospheric oscillations. We identify several types of spectra that can fit long-baseline reactor and accelerator neutrino oscillation data, but fail in explaining solar and/or atmospheric data. The only two solutions that survive are the expected seesaw and quasi-Dirac regions, for which we set lower and upper bounds respectively on the Majorana mass scale. Solar data from neutral current measurements provide essential information to constrain the quasi-Dirac region. The possibility to accommodate the LSND/MiniBoone and reactor anomalies, and the implications for neutrinoless double-beta decay and tritium beta decay are briefly discussed. |
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1126-6708 |
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WOS:000293741500041 |
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no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ elepoucu @ |
Serial |
760 |
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Author |
Hernandez, P.; Kekic, M.; Lopez-Pavon, J. |
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Title |
Low-scale seesaw models versus N-eff |
Type |
Journal Article |
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Year |
2014 |
Publication |
Physical Review D |
Abbreviated Journal |
Phys. Rev. D |
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Volume |
89 |
Issue |
7 |
Pages |
073009 - 7pp |
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We consider the contribution of the extra sterile states in generic low-scale seesaw models to extra radiation, parametrized by N-eff. We find that the value of Neff is roughly independent of the seesaw scale within a wide range. We explore the full parameter space in the case of two extra sterile states and find that these models are strongly constrained by cosmological data for any value of the seesaw scale below O(100 MeV). |
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Address |
[Hernandez, P.; Kekic, M.] IFIC CSIC UVEG, E-46071 Valencia, Spain |
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Amer Physical Soc |
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English |
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1550-7998 |
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Notes |
WOS:000334317200005 |
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no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
1754 |
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Author |
Hernandez, P.; Kekic, M.; Lopez-Pavon, J. |
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Title |
N_eff in low-scale seesaw models versus the lightest neutrino mass |
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Journal Article |
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Year |
2014 |
Publication |
Physical Review D |
Abbreviated Journal |
Phys. Rev. D |
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Volume |
90 |
Issue |
6 |
Pages |
065033 - 12pp |
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We evaluate the contribution to N_eff of the extra sterile states in low-scale type I seesaw models (with three extra sterile states). We explore the full parameter space and find that at least two of the heavy states always reach thermalization in the early Universe, while the third one might not thermalize provided the lightest neutrino mass is below O(10(-3) eV). Constraints from cosmology therefore severely restrict the spectra of heavy states in the range 1 eV-100 MeV. The implications for neutrinoless double beta decay are also discussed. |
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[Hernandez, P.; Kekic, M.] Univ Valencia, IFIC CSIC, E-46071 Valencia, Spain, Email: m.pilar.hernandez@uv.es; |
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Amer Physical Soc |
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English |
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1550-7998 |
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Notes |
WOS:000344108100004 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
2001 |
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Author |
Caputo, A.; Hernandez, P.; Kekic, M.; Lopez-Pavon, J.; Salvado, J. |
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Title |
The seesaw path to leptonic CP violation |
Type |
Journal Article |
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Year |
2017 |
Publication |
European Physical Journal C |
Abbreviated Journal |
Eur. Phys. J. C |
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Volume |
77 |
Issue |
4 |
Pages |
258 - 7pp |
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Abstract |
Future experiments such as SHiP and highintensity e(+)e(-) colliders will have a superb sensitivity to heavy Majorana neutrinos with masses below M-Z. We show that the measurement of the mixing to electrons and muons of one such state could establish the existence of CP violating phases in the neutrino mixing matrix, in the context of low-scale seesaw models. We quantify in the minimal model the CP reach of these future experiments, and demonstrate that CP violating phases in the mixing matrix could be established at 5 sigma CL in a very significant fraction of parameter space. |
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[Caputo, A.; Hernandez, P.; Kekic, M.; Salvado, J.] Univ Valencia, Inst Fis Corpuscular, Edificio Inst Invest,Catedrat Jose Beltran 2, Paterna 46980, Spain, Email: andrea.caputo@cern.ch; |
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Springer |
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English |
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ISSN |
1434-6044 |
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Notes |
WOS:000400079300002 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
3111 |
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Author |
Drewes, M.; Garbrecht, B.; Hernandez, P.; Kekic, M.; Lopez-Pavon, J.; Racker, J.; Rius, N.; Salvado, J.; Teresi, D. |
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Title |
ARS leptogenesis |
Type |
Journal Article |
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Year |
2018 |
Publication |
International Journal of Modern Physics A |
Abbreviated Journal |
Int. J. Mod. Phys. A |
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Volume |
33 |
Issue |
5-6 |
Pages |
1842002 - 46pp |
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Abstract |
We review the current status of the leptogenesis scenario originally proposed by Akhmedov, Rubakov and Smirnov (ARS). It takes place in the parametric regime where the right-handed neutrinos are at the electroweak scale or below and the CP-violating effects are induced by the coherent superposition of different right-handed mass eigenstates. Two main theoretical approaches to derive quantum kinetic equations, the Hamiltonian time evolution as well as the Closed-Time-Path technique are presented, and we discuss their relations. For scenarios with two right-handed neutrinos, we chart the viable parameter space. Both, a Bayesian analysis, that determines the most likely configurations for viable leptogenesis given different variants of flat priors, and a determination of the maximally allowed mixing between the light, mostly left-handed, and heavy, mostly right-handed, neutrino states are discussed. Rephasing invariants are shown to be a useful tool to classify and to understand various distinct contributions to ARS leptogenesis that can dominate in different parametric regimes. While these analyses are carried out for the parametric regime where initial asymmetries are generated predominantly from lepton-number conserving, but flavor violating effects, we also review the contributions from lepton-number violating operators and identify the regions of parameter space where these are relevant. |
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Address |
[Drewes, M.; Garbrecht, B.] Tech Univ Munich, Phys Dept, James Franck Str, D-85748 Garching, Germany, Email: m.pilar.hernandez@uv.es |
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World Scientific Publ Co Pte Ltd |
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English |
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Edition |
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ISSN |
0217-751x |
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Notes |
WOS:000426586100003 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
3508 |
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