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Non-decoupling of heavy neutrinos and lepton flavour violation
We consider a class of models predicting new heavy neutral fermionic states, whose mixing with the light neutrinos can be naturally significant and produce observable effects below the threshold for their production. We update the indirect limits on the flavour non-diagonal mixing parameters that ca...
Autores principales: | , , , |
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Lenguaje: | eng |
Publicado: |
1995
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Materias: | |
Acceso en línea: | https://dx.doi.org/10.1016/0550-3213(95)00201-3 http://cds.cern.ch/record/277936 |
_version_ | 1780887683043688448 |
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author | Tommasini, D. Barenboim, G. Bernabeu, J. Jarlskog, C. |
author_facet | Tommasini, D. Barenboim, G. Bernabeu, J. Jarlskog, C. |
author_sort | Tommasini, D. |
collection | CERN |
description | We consider a class of models predicting new heavy neutral fermionic states, whose mixing with the light neutrinos can be naturally significant and produce observable effects below the threshold for their production. We update the indirect limits on the flavour non-diagonal mixing parameters that can be derived from unitarity, and show that significant rates are in general expected for one-loop-induced rare processes due to the exchange of virtual heavy neutrinos, involving the violation of the muon and electron lepton numbers. In particular, the amplitudes for \mu--e conversion in nuclei and for \mu\to ee^+e^- show a non-decoupling quadratic dependence on the heavy neutrino mass M, while \mu\to e\gamma is almost independent of the heavy scale above the electroweak scale. These three processes are then used to set stringent constraints on the flavour-violating mixing angles. In all the cases considered, we point out explicitly that the non-decoupling behaviour is strictly related to the spontaneous breaking of the SU(2) symmetry. |
id | cern-277936 |
institution | Organización Europea para la Investigación Nuclear |
language | eng |
publishDate | 1995 |
record_format | invenio |
spelling | cern-2779362020-09-26T02:14:21Zdoi:10.1016/0550-3213(95)00201-3http://cds.cern.ch/record/277936engTommasini, D.Barenboim, G.Bernabeu, J.Jarlskog, C.Non-decoupling of heavy neutrinos and lepton flavour violationParticle Physics - PhenomenologyWe consider a class of models predicting new heavy neutral fermionic states, whose mixing with the light neutrinos can be naturally significant and produce observable effects below the threshold for their production. We update the indirect limits on the flavour non-diagonal mixing parameters that can be derived from unitarity, and show that significant rates are in general expected for one-loop-induced rare processes due to the exchange of virtual heavy neutrinos, involving the violation of the muon and electron lepton numbers. In particular, the amplitudes for \mu--e conversion in nuclei and for \mu\to ee^+e^- show a non-decoupling quadratic dependence on the heavy neutrino mass M, while \mu\to e\gamma is almost independent of the heavy scale above the electroweak scale. These three processes are then used to set stringent constraints on the flavour-violating mixing angles. In all the cases considered, we point out explicitly that the non-decoupling behaviour is strictly related to the spontaneous breaking of the SU(2) symmetry.We consider a class of models predicting new heavy neutral fermionic states, whose mixing with the light neutrinos can be naturally significant and produce observable effects below the threshold for their production. We update the indirect limits on the flavour non-diagonal mixing parameters that can be derived from unitarity, and show that significant rates are in general expected for one-loop-induced rare processes due to the exchange of virtual heavy neutrinos, involving the violation of the muon and electron lepton numbers. In particular, the amplitudes for μ - e conversion in nuclei and for μ → ee + e − show a non-decoupling quadratic dependence on the heavy neutrino mass M , while μ → eγ is almost independent of the heavy scale above the electroweak scale. These three processes are then used to set stringent constraints on the flavour-violating mixing angles. In all the cases considered, we point out explicitly that the non-decoupling behaviour is strictly related to the spontaneous breaking of the SU(2) symmetry.We consider a class of models predicting new heavy neutral fermionic states, whose mixing with the light neutrinos can be naturally significant and produce observable effects below the threshold for their production. We update the indirect limits on the flavour non-diagonal mixing parameters that can be derived from unitarity, and show that significant rates are in general expected for one-loop-induced rare processes due to the exchange of virtual heavy neutrinos, involving the violation of the muon and electron lepton numbers. In particular, the amplitudes for $\mu$--$e$ conversion in nuclei and for $\mu\to ee^+e^-$ show a non-decoupling quadratic dependence on the heavy neutrino mass $M$, while $\mu\to e\gamma$ is almost independent of the heavy scale above the electroweak scale. These three processes are then used to set stringent constraints on the flavour-violating mixing angles. In all the cases considered, we point out explicitly that the non-decoupling behaviour is strictly related to the spontaneous breaking of the SU(2) symmetry.hep-ph/9503228CERN-TH-95-33CERN-TH-95-033FTUV-95-10IFIC-95-10LUND-MPH-95-03UM-TH-95-10CERN-TH-95-33FTUV-95-10IFIC-95-10LUND-MPH-95-03UM-TH-95-10oai:cds.cern.ch:2779361995-03-03 |
spellingShingle | Particle Physics - Phenomenology Tommasini, D. Barenboim, G. Bernabeu, J. Jarlskog, C. Non-decoupling of heavy neutrinos and lepton flavour violation |
title | Non-decoupling of heavy neutrinos and lepton flavour violation |
title_full | Non-decoupling of heavy neutrinos and lepton flavour violation |
title_fullStr | Non-decoupling of heavy neutrinos and lepton flavour violation |
title_full_unstemmed | Non-decoupling of heavy neutrinos and lepton flavour violation |
title_short | Non-decoupling of heavy neutrinos and lepton flavour violation |
title_sort | non-decoupling of heavy neutrinos and lepton flavour violation |
topic | Particle Physics - Phenomenology |
url | https://dx.doi.org/10.1016/0550-3213(95)00201-3 http://cds.cern.ch/record/277936 |
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