Dirac vs. Majorana HNLs (and their oscillations) at SHiP
Abstract SHiP is a proposed high-intensity beam dump experiment set to operate at the CERN SPS. It is expected to have an unprecedented sensitivity to a variety of models containing feebly interacting particles, such as Heavy Neutral Leptons (HNLs). Two HNLs or more could successfully explain the ob...
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| Format: | Article |
| Language: | English |
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SpringerOpen
2020-04-01
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| Series: | Journal of High Energy Physics |
| Subjects: | |
| Online Access: | http://link.springer.com/article/10.1007/JHEP04(2020)005 |
| _version_ | 1817977647430369280 |
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| author | J.-L. Tastet I. Timiryasov |
| author_facet | J.-L. Tastet I. Timiryasov |
| author_sort | J.-L. Tastet |
| collection | DOAJ |
| description | Abstract SHiP is a proposed high-intensity beam dump experiment set to operate at the CERN SPS. It is expected to have an unprecedented sensitivity to a variety of models containing feebly interacting particles, such as Heavy Neutral Leptons (HNLs). Two HNLs or more could successfully explain the observed neutrino masses through the seesaw mechanism. If, in addition, they are quasi-degenerate, they could be responsible for the baryon asymmetry of the Universe. Depending on their mass splitting, HNLs can have very different phenomenologies: they can behave as Majorana fermions — with lepton number violating (LNV) signatures, such as same-sign dilepton decays — or as Dirac fermions with only lepton number conserving (LNC) signatures. In this work, we quantitatively demonstrate that LNV processes can be distinguished from LNC ones at SHiP, using only the angular distribution of the HNL decay products. Accounting for spin correlations in the simulation and using boosted decision trees for discrimination, we show that SHiP will be able to distinguish Majorana-like and Dirac-like HNLs in a significant fraction of the currently unconstrained parameter space. If the mass splitting is of order 10 −6 eV, SHiP could even be capable of resolving HNL oscillations, thus providing a direct measurement of the mass splitting. This analysis highlights the potential of SHiP to not only search for feebly interacting particles, but also perform model selection. |
| first_indexed | 2024-04-13T22:19:27Z |
| format | Article |
| id | doaj.art-a3c2acafd49342a88f283a29edeb0dbe |
| institution | Directory Open Access Journal |
| issn | 1029-8479 |
| language | English |
| last_indexed | 2024-04-13T22:19:27Z |
| publishDate | 2020-04-01 |
| publisher | SpringerOpen |
| record_format | Article |
| series | Journal of High Energy Physics |
| spelling | doaj.art-a3c2acafd49342a88f283a29edeb0dbe2022-12-22T02:27:21ZengSpringerOpenJournal of High Energy Physics1029-84792020-04-012020413810.1007/JHEP04(2020)005Dirac vs. Majorana HNLs (and their oscillations) at SHiPJ.-L. Tastet0I. Timiryasov1Discovery Center, Niels Bohr Institute, University of CopenhagenInstitute of Physics, Laboratory for Particle Physics and Cosmology, École Polytechnique Fédérale de LausanneAbstract SHiP is a proposed high-intensity beam dump experiment set to operate at the CERN SPS. It is expected to have an unprecedented sensitivity to a variety of models containing feebly interacting particles, such as Heavy Neutral Leptons (HNLs). Two HNLs or more could successfully explain the observed neutrino masses through the seesaw mechanism. If, in addition, they are quasi-degenerate, they could be responsible for the baryon asymmetry of the Universe. Depending on their mass splitting, HNLs can have very different phenomenologies: they can behave as Majorana fermions — with lepton number violating (LNV) signatures, such as same-sign dilepton decays — or as Dirac fermions with only lepton number conserving (LNC) signatures. In this work, we quantitatively demonstrate that LNV processes can be distinguished from LNC ones at SHiP, using only the angular distribution of the HNL decay products. Accounting for spin correlations in the simulation and using boosted decision trees for discrimination, we show that SHiP will be able to distinguish Majorana-like and Dirac-like HNLs in a significant fraction of the currently unconstrained parameter space. If the mass splitting is of order 10 −6 eV, SHiP could even be capable of resolving HNL oscillations, thus providing a direct measurement of the mass splitting. This analysis highlights the potential of SHiP to not only search for feebly interacting particles, but also perform model selection.http://link.springer.com/article/10.1007/JHEP04(2020)005Beyond Standard ModelNeutrino Physics |
| spellingShingle | J.-L. Tastet I. Timiryasov Dirac vs. Majorana HNLs (and their oscillations) at SHiP Journal of High Energy Physics Beyond Standard Model Neutrino Physics |
| title | Dirac vs. Majorana HNLs (and their oscillations) at SHiP |
| title_full | Dirac vs. Majorana HNLs (and their oscillations) at SHiP |
| title_fullStr | Dirac vs. Majorana HNLs (and their oscillations) at SHiP |
| title_full_unstemmed | Dirac vs. Majorana HNLs (and their oscillations) at SHiP |
| title_short | Dirac vs. Majorana HNLs (and their oscillations) at SHiP |
| title_sort | dirac vs majorana hnls and their oscillations at ship |
| topic | Beyond Standard Model Neutrino Physics |
| url | http://link.springer.com/article/10.1007/JHEP04(2020)005 |
| work_keys_str_mv | AT jltastet diracvsmajoranahnlsandtheiroscillationsatship AT itimiryasov diracvsmajoranahnlsandtheiroscillationsatship |