402 research outputs found
Type II leptogenesis and the neutrino mass scale
No full textWe discuss the effect of the neutrino mass scale on baryogenesis via the out-of-equilibrium decay of the lightest right-handed (s)neutrinos in type II see–saw models. We calculate the type II contributions to the decay asymmetries for minimal scenarios based on the Standard Model and on the Minimal Supersymmetric Standard Model, where the additional direct mass term for the neutrinos arises from a Higgs triplet vacuum expectation value. The result in the supersymmetric case is new and we correct the previous result in the scenario based on the Standard Model. We confirm and generalize our results by calculating the decay asymmetries in an effective approach, which is independent of the realization of the type II contribution. We derive a general upper bound on the decay asymmetry in type II see–saw models and find that it increases with the neutrino mass scale, in sharp contrast to the type I case which leads to an upper bound of about 0.1 eV on the neutrino mass scale. We find a lower bound on the mass of the lightest right-handed neutrino, significantly below the corresponding type I bound for partially degenerate neutrinos. This lower bound decreases with increasing neutrino mass scale, making leptogenesis more consistent with the gravitino constraints in supersymmetric models
Lepton flavour violation in the constrained MSSM with constrained sequential dominance
No full textWe consider charged lepton flavour violation (LFV) in the constrained minimal supersymmetric Standard Model, extended to include the see-saw mechanism with constrained sequential dominance (CSD), where CSD provides a natural see-saw explanation of tri-bimaximal neutrino mixing. When charged lepton corrections to tri-bimaximal neutrino mixing are included, we discover characteristic correlations among the LFV branching ratios, depending on the mass ordering of the right-handed neutrinos, with a pronounced dependence on the leptonic mixing angle ?13 (and in some cases also on the Dirac CP phase ?).<br/
Charged lepton corrections to neutrino mixing angles and CP phases revisited
No full textWe re-analyze charged lepton corrections to neutrino mixing angles and CP phases, carefully including CP phases from the charged lepton sector. We present simple analytical formulae for including the charged lepton corrections and derive compact new results for small neutrino and charged lepton mixings View the MathML source and View the MathML source. We find a generic relation View the MathML source, which relates the prediction from the neutrino sector View the MathML source to the charged lepton mixing View the MathML source and to the MNS neutrino oscillation phase ?. We apply our formula to the examples of bimaximal or tri-bimaximal neutrino mixing. One implication is that the so-called quark–lepton complementarity relation ?12+?C=45° can only hold for ?=? and it gets modified in the presence of leptonic CP violation. On the other hand, the lepton mixing ?13 generated from the charged lepton correction View the MathML source is independent of CP phases and given by View the MathML source. Combining these results leads to a model-independent sum rule: View the MathML source where View the MathML source in the case of (tri-)bimaximal neutrino mixing, for example
Research on poly(ether ketone ketone) PEEK based composites
No full textDer Datensatz beschreibt die Herstellung und Charakterisierung von PEEK-basierten Kompositen.The dataset describes the production and characterization of PEEK-based composites.Die Forschungsdaten gehöre zur folgenden Publikation:
T. Hanemann, A. Klein, S. Baumgärtner, J. Jung, D. Wilhelm, S. Antusch, Material Extrusion 3D Printing of PEEK-Based Composites, Polymers, 15(16), 3412 (2023), DOI: 10.3390/polym15163412
Neutrino mixing from the charged lepton sector with sequential right-handed lepton dominance
No full textWe systematically analyze the possibility that bi-large lepton mixing originates from the charged lepton sector in models with sequential dominance for the right-handed charged leptons. We derive analytical expressions for the mixing angles and CP phases of the MNS matrix for the case of zero mixing from the neutrino sector, which is arranged for with the help of sequential dominance for the right-handed neutrinos. For small ?13, the two large mixing angles ?12 and ?23 are determined by the Yukawa couplings to the dominant right-handed tau. The mixing angle ?13 is then governed by the subdominant right-handed muon Yukawa couplings. Naturally small ?13 and sequential right-handed lepton dominance can be realized in type I see-saw models and their type II upgrades via spontaneously broken SO(3) flavour symmetry and real vacuum alignment. We discuss the prediction for ?13 in this scenario and corrections to it including the dependence on the neutrino mass scale
Neutrino mixing angles in sequential dominance to NLO and NNLO
No full textNeutrinos with hierarchical masses and two large mixing angles may naturally originate from sequential dominance (SD). Within this framework we present analytic expressions for the neutrino mixing angles including the next-to-leading order (NLO) and next-to-next-to-leading order (NNLO) corrections arising from the second lightest and lightest neutrino masses. The analytic results for neutrino mixing angles in SD presented here, including the NLO and NNLO corrections, are applicable to a wide class of models and may provide useful insights when confronting the models with data from high precision neutrino experiments. We also point out that for special cases of SD corresponding to form dominance (FD) the NLO and NNLO corrections both vanish. For example we study tri-bimaximal (TB) mixing via constrained sequential dominance (CSD) which involves only a NNLO correction and tri-bimaximal-reactor (TBR) mixing via partially constrained sequential dominance (PCSD) which involves a NLO correction suppressed by the small reactor angle and show that the analytic results have good agreement with the numerical results for these cases
Flavour-dependent leptogenesis with sequential dominance
No full textWe study thermal leptogenesis in classes of neutrino mass models based on the seesaw mechanism with three right-handed neutrinos and sequential right-handed neutrino dominance. The flavour-dependent Boltzmann equations are solved appropriately to both the Standard Model and the Minimal Supersymmetric Standard Model. Within these classes of models we investigate constraints and expectations on the individual decay asymmetries and wash-out parameters from the present data on neutrino masses and mixings. In many cases of physical interest, flavour effects are shown to have important consequences for the estimation of the baryon asymmetry produced in leptogenesis. We also establish and analyse the link between the leptonic CP violating phase ?, observable in neutrino oscillations, and the CP violation required for leptogenesis, where flavour-dependent effects have a significant effect. In general our results show that flavour-dependent effects cannot be ignored when dealing with three right-handed neutrino models
Sequential dominance
No full textWe review the mechanism of sequential right-handed neutrino dominance proposed in the framework of the type I see-saw mechanism to account for bi-large neutrino mixing and a neutrino mass hierarchy in a natural way. We discuss how sequential dominance (SD) may also be applied to the right-handed charged leptons, which alternatively allows for bi-large lepton mixing from the charged lepton sector. We review how such SD models may be upgraded to include type II see-saw contributions, resulting in a partially degenerate neutrino mass spectrum with the bi-large lepton mixing arising from SD. We also summarize the model-building applications and the phenomenological implications of SD
Quark lepton complementarity in unified theories
No full textAs pointed out by many authors, recent observations are consistent with an intriguing relation between the Cabibbo angle θC and the solar neutrino mixing angle θ12, namely θ12 ~ π/4 - θC. Such quark–lepton complementarity (QLC) may be a signal of an underlying quark–lepton unification at short distances. We discuss possible ways to realize this relation in realistic quark–lepton unification theories by identifying a minimal set of operators that lead to QLC while remaining consistent with other known data. The purpose of this Letter is to present the first elements of a unified model at the GUT scale capable of predicting the QLC relation. A generic prediction of our proposed class of models is the new relation for the lepton mixing angle θ13 ~ θC, which allows these models to be confirmed or excluded by the current generation of neutrino oscillation experiments
Measurable neutrino mass scale in <i>A<sub>4</sub> × SU(5)</i>
No full textWe propose a supersymmetric A4 × SU(5) model of quasidegenerate neutrinos which predicts the effective neutrino mass mee relevant for neutrinoless double beta decay to be proportional to the neutrino mass scale, thereby allowing its determination approximately independently of unknown Majorana phases. Such a natural quasidegeneracy is achieved by using A4 family symmetry (as an example of a non-Abelian family symmetry with real triplet representations) to enforce a contribution to the neutrino mass matrix proportional to the identity. Tribimaximal neutrino mixing as well as quark CP violation with α ≈ 90° and a leptonic CP phase δMNS ≈ 90° arise from the breaking of the A4 family symmetry by the vacuum expectation values of four “flavon” fields pointing in specific postulated directions in flavor space
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