Global bounds on the Type-III Seesaw
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Springer
Received: December 18, Revised: February 25, Accepted: March 25, Published: May 6,
2019 2020 2020 2020
Global bounds on the Type-III Seesaw
a
Dipartimento di Fisica, Universit` a di Genova and INFN — Sezione di Genova, via Dodecaneso 33, 16146 Genova, Italy b Instituto de F´ısica Te´ orica UAM/CSIC, Calle Nicol´ as Cabrera 13-15, Cantoblanco E-28049 Madrid, Spain c Departamento de F´ısica Te´ orica, Universidad Aut´ onoma de Madrid, Cantoblanco E-28049 Madrid, Spain d Institute for Theoretical Physics, ELTE E¨ otv¨ os Lor´ and University, P´ azm´ any P´eter s´et´ any 1/A, H-1117 Budapest, Hungary e Instituto de F´ısica Corpuscular, Universidad de Valencia and CSIC, Edificio Institutos Investigaci´ on, Catedr´ atico Jos´e Beltr´ an 2, 46980, Spain
E-mail: [email protected], [email protected], [email protected], [email protected], [email protected] Abstract: We derive general bounds on the Type-III Seesaw parameters from a global fit to flavor and electroweak precision data. We explore and compare three Type-III Seesaw realizations: a general scenario, where an arbitrary number of heavy triplets is integrated out without any further assumption, and the more constrained cases in which only 3 or 2 (minimal scenario) additional heavy states are included. The latter assumption implies rather non-trivial correlations in the Yukawa flavor structure of the model so as to reproduce the neutrino masses and mixings as measured in neutrino oscillations experiments and thus qualitative differences can be found with the more general scenario. In particular, we find that, while the bounds on most elements of the dimension 6 operator coefficients are of order 10−4 for the general and 3-triplet cases, the 2-triplet scenario is more strongly constrained with bounds between 10−5 and 10−7 for the different flavours. We also discuss how these correlations affect the present CMS constraints on the Type-III Seesaw in the minimal 2-triplet scenario. Keywords: Neutrino Physics, Beyond Standard Model ArXiv ePrint: 1911.11790
c The Authors. Open Access, Article funded by SCOAP3 .
https://doi.org/10.1007/JHEP05(2020)022
JHEP05(2020)022
Carla Biggio,a Enrique Fernandez-Martinez,b,c Manuele Filaci,a Josu Hernandez-Garciad and Jacobo Lopez-Pavone
Contents 1 Introduction
1
2 Type-III Seesaw scenarios and parametrization
2
General scenario (G-SS)
4
2.2
Three triplets Seesaw scenario (3Σ-SS)
4
2.3
Two triplets Seesaw scenario (2Σ-SS)
6
3 Observables
7
3.1
Constraints from µ-decay: MW and θW
8
3.2
Constraints from Z decays
9
3.2.1
Invisible Z decay
9
3.2.2
Z decays into charged fermions
9
3.2.3
Z asymmetry parameters
10
3.3
Constraints from weak interaction universality tests
11
3.4
Unitarity of the CKM matrix
12
3.4.1
12 15
3.5.2
µ → e conversion in nuclei
LFV 3-body lepton decays
15
3.5.3
LFV Z and h decays
15
3.5.4
Radiative decays
16
LFV observables 3.5.1
3.6
12
Determination of |Vus |
3.4.2 3.5
Determination of |Vud | via Superallowed
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