Vinzenz Maurer

Large neutrino mixing angle

We analyse how a large value of the leptonic mixing angle \theta_{13}^{MNS} can be generated via charged lepton corrections in unified flavour models, using novel combinations of Clebsch-Gordan factors for obtaining viable quark-lepton mass ratios for the first two families. We discuss how these Clebsch-Gordan factors affect the relations between down-type quark mixing and charged lepton mixing in SU(5) GUTs and Pati-Salam unified models and calculate the resulting possible predictions for \theta_{13}^{MNS} for models with \theta_{13}^\nu, \theta_{13}^e << \theta_{12}^e. While symmetric mass matrices with zero (1,1)-elements always lead to comparatively small \theta_{13}^{MNS} \approx 2.8 degrees, we find novel combinations of Clebsch-Gordan factors for non-symmetric mass matrices which can yield \theta_{13}^{MNS} \approx 5.1 degrees, 6.1 degrees, 7.6 degrees or 10.1 degrees, as favoured by the current experimental hints for large \theta_{13}^{MNS}. We discuss applications to classes of models with underlying tri-bimaximal or bimaximal mixing in the neutrino sector.

\theta_{13}

A bstractWe calculate the values and 1σ ranges of the running quark and lepton Yukawa couplings as well as of the quark mixing parameters at various energy scales, i.e. at MZ, 1 TeV, 3 TeV, 10 TeV and at the GUT scale, to provide useful input for model building. Above TeV energies, we assume the minimal supersymmetric extension of the Standard Model, and include the tan β-enhanced one-loop supersymmetric threshold corrections which arise when matching the SM to its SUSY extension. We calculate the GUT scale values of the running parameters as well as their 1σ ranges, with the supersymmetric threshold corrections included and with their effects parametrised in a simple way.

^{MNS} and quark-lepton mass ratios in unified flavour models

A bstractWe analyse the naturalness of the Minimal Supersymmetric Standard Model (MSSM) in the light of recent LHC results from the ATLAS and CMS experiments. We study non-universal boundary conditions for the scalar and the gaugino sector, with fixed relations between some of the soft breaking parameters, and find a significant reduction of fine-tuning for non-universal gaugino masses. For a Higgs mass of about 125 GeV, as observed recently, we find parameter regions with a fine-tuning of O (10), taking into account experimental and theoretical uncertainties. These regions also survive after comparison with simplified model searches in ATLAS and CMS. For a fine-tuning less than 20 the lightest neutralino is expected to be lighter than about 400 GeV and the lighter stop can be as heavy as 3.5TeV. On the other hand, the gluino mass is required to be above 1.5 TeV. For non-universal gaugino masses, we discuss which fixed GUT scale ratios can lead to a reduced fine-tuning and find that the recent Higgs results have a strong impact on which ratio is favoured. We also discuss the naturalness of GUT scale Yukawa relations, comparing the non-universal MSSM with the CMSSM.

Running quark and lepton parameters at various scales

Abstract The recent observations of the leptonic mixing angle θ 13 PMNS are consistent with θ 13 PMNS = θ C / 2 (with θ C being the Cabibbo angle θ 12 CKM ). We discuss how this relation can emerge in Grand Unified Theories (GUTs) via charged lepton corrections. The key ingredient is that in GUTs the down-type quark Yukawa matrix and the charged lepton Yukawa matrix are generated from the same set of GUT operators, which implies that the resulting entries are linked and differ only by group-theoretical Clebsch factors. This allows a link θ 12 e ≈ θ C to be established, which can induce θ 13 PMNS ≈ θ C / 2 provided that the 1–3 mixing in the neutrino mass matrix is much smaller than θ C . We find simple conditions under which θ 13 PMNS ≈ θ C / 2 can arise via this link in SU(5) GUTs and Pati–Salam models. We also discuss possible corrections to the exact relation. Using lepton mixing sum rules different neutrino mixing patterns can be distinguished by their predictions for the Dirac CP phase δ PMNS .

Naturalness of the Non-Universal MSSM in the light of the recent Higgs results

We propose a supersymmetric SU(5) GUT model with an A_4 family symmetry - including a full flavon- and messenger sector - which realises the relation theta_13^PMNS \simeq theta_C / sqrt(2). The neutrino sector features tri-bimaximal mixing, and theta_13^PMNS \simeq theta_C / sqrt(2) emerges from the charged lepton contribution to the PMNS matrix, which in turn is linked to quark mixing via specific GUT relations. These GUT relations arise after GUT symmetry breaking from a novel combination of group theoretical Clebsch-Gordan factors, which in addition to large theta_13^PMNS lead to promising quark lepton mass ratios for all generations of quarks and leptons and to m_s / m_d = 18.95_(-0.24)^(+0.33), in excellent agreement with experimental results. The model also features spontaneous CP violation, with all quark and lepton CP phases determined from family symmetry breaking. We perform a full Markov Chain Monte Carlo fit to the available quark and lepton data, and discuss how the model can be tested by present and future experiments.

\theta^PMNS_13 = \theta_C / \sqrt2 from GUTs

A bstractTwo puzzling facts of our time are the observed patterns in the fermion masses and mixings and the existence of non-baryonic dark matter, which are both often associated with extensions of the Standard Model at higher energy scales. In this paper, we consider a solution to these two problems with the flavour symmetry A4×ℤ2×ℤ2′

\( {\mathbb{A}}_4 \) symmetry at colliders and in the universe

{\mathbb{A}}_4\times {\mathrm{\mathbb{Z}}}_2\times {\mathrm{\mathbb{Z}}}_2^{\prime }

Naturalness and GUT Scale Yukawa Coupling Ratios in the CMSSM

, in a model which has been shown before to explain large leptonic mixings with a specific texture. The model contains 3 generations of SU(2)L-doublet scalar fields, arranged as an A4