Seesaw mechanisms for Dirac and Majorana neutrino masses

Abstract. We study models in which neutrino masses are generated dynamically at cosmologically late times. Our study is purely phenomenological and parameterized in terms of three effective parameters characterizing the redshift of mass generation, the width of the transition region, and the present day neutrino mass. We also study the possibility that neutrinos become strongly selfinteracting at the time where the mass is generated. We find that in a number of cases, models with large present day neutrino masses are allowed by current CMB, BAO and supernova data. The increase in the allowed mass range makes it possible that a non-zero neutrino mass could be measured in direct detection experiments such as KATRIN. Intriguingly we also find that there are allowed models in which neutrinos become strongly self-interacting around the epoch of recombination.

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“…This can be understood by looking at the expression for the CMB temperature multipoles, Θ l , (see e.g. equation 8.55 in [20]):…”

Section: Effects Of Neutrino Massesmentioning

confidence: 99%

Constraining dynamical neutrino mass generation with cosmological data

Koksbang

Hannestad

2017

J. Cosmol. Astropart. Phys.

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“…where M 1 is supposed to contain the light masses and M 2 the heavy ones (see [6], paragraph IIB). One finds…”

Section: ( )mentioning

confidence: 99%

A remark on the mathematics of the seesaw mechanism

Besnard¹

2017

J. Phys. Commun.

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To demonstrate that matrices of seesaw type lead to a hierarchy in the neutrino masses, i.e. that there is a large gap in the singular spectrum of these matrices, one generally uses an approximate blockdiagonalization procedure. In this note we show that no approximation is required to prove this gap property if the Courant-Fisher-Weyl theorem is used instead. This simple observation might not be original, however it does not seem to show up in the literature. We also sketch the proof of additional inequalities for the singular values of matrices of seesaw type.

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“…Rather, it can be much heavier than other particles. The seesaw mechanism [13] can naturally give rise to light neutrinos. When a left-handed neutrino interacts with the Higgs boson, it acquires a mass, m, which is comparable to the mass of other quarks and leptons.…”

Section: Majorana Neutrinosmentioning

confidence: 99%

“…7. 13. Instead of using a matrix element generator for the W + jets processes (like Alpgen [151]), a simplified approach is pursued: The available inclusive Pythia W → eν samples containing events with higher jet multiplicities are reweighted.…”

Section: Trigger Efficiencymentioning

confidence: 99%

Search for new heavy charged gauge bosons

Magass¹,

Hebbeker²

2007

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Additional gauge bosons are introduced in many theoretical extensions to the Standard Model. A search for a new heavy charged gauge boson W ′ decaying into an electron and a neutrino is presented. The data used in this analysis was taken with the DØ detector at the Fermilab proton-antiproton collider at a center-of-mass energy of 1.96 TeV and corresponds to an integrated luminosity of about 1 fb −1 . Since no significant excess is observed in the data, an upper limit is set on the production cross section times branching fraction σ W ′ ×Br (W ′ → eν). Using this limit, a W ′ boson with mass below ∼1 TeV can be excluded at the 95% confidence level assuming that the new boson has the same couplings to fermions as the Standard Model W boson. Search for New Heavy Charged Gauge BosonsAdditional gauge bosons (including the equivalent to the Z, the Z ′ ) are introduced in many extensions to the Standard Model of particle physics. Assuming the most general case, the new gauge group can comprise a new mixing angle and new couplings. Here, the Altarelli Reference Model is considered which represents a generalization of the Manifest Left-Right Symmetric Model with light right-handed neutrinos. This model makes the assumptions that the new gauge boson W ′ has the same couplings as the Standard Model W boson and that there is no mixing. Hence, the W ′ is a heavy copy of the Standard Model W boson.The clear decay signature (in analogy to the decay of the W ) contains an isolated electron with extreme high energy which is important for triggering. The neutrino can not be detected, but it gives rise to missing energy in the detector. The Jacobian peak in the transverse mass distribution stemming from the W decay is used for calibration, whereas the tail of the transverse mass distribution is searched for a possible W ′ signal.The data agrees with the expectation from background processes. For instance, in the data 37 events are reconstructed with transverse masses above 300 GeV compared to a prediction of 37.1 ± 2.1 (stat) +6.0 −3.7 (sys) background events. Since no significant excess is found in the data, an upper limit is set on the production cross section for heavy charged gauge bosons decaying into electron and neutrino, σ W ′ × Br (W ′ → eν). Using this limit, a lower bound on the mass of the new gauge boson can be derived at the 95% confidence level,

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Seesaw mechanisms for Dirac and Majorana neutrino masses

Cited by 23 publications

References 45 publications

Constraining dynamical neutrino mass generation with cosmological data

Constraining dynamical neutrino mass generation with cosmological data

A remark on the mathematics of the seesaw mechanism

Search for new heavy charged gauge bosons

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