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Dive into the research topics where Martin Holthausen is active.

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Featured researches published by Martin Holthausen.


Journal of High Energy Physics | 2013

CP and discrete flavour symmetries

Martin Holthausen; Manfred Lindner; Michael A. Schmidt

A bstractWe give a consistent definition of generalised CP transformations in the context of discrete flavour symmetries. Non-trivial consistency conditions imply that every generalised CP transformation can be interpreted as a representation of an automorphism of the discrete group. This allows us to give consistent generalised CP transformations of popular flavour groups. We are able to clear up issues concerning recent claims about geometrical CP violation in models based on T′, clarify the origin of ”calculable phases” in Δ(27) and explain why apparently CP violating scalar potentials of A4 result in a CP conserving ground state.


Nuclear Physics | 2015

Higgs →μτ in Abelian and non-Abelian flavor symmetry models

Julian Heeck; Martin Holthausen; Werner Rodejohann; Yusuke Shimizu

We study lepton flavor violating Higgs decays in two models, with the recently found hint for Higgs→μτ at CMS as a benchmark value for the branching ratio. The first model uses the discrete flavor symmetry group A4, broken at the electroweak scale, while the second is renormalizable and based on the Abelian gauge group Lμ−Lτ. Within the models we find characteristic predictions for other non-standard Higgs decay modes, charged lepton flavor violating decays and correlations of the branching ratios with neutrino oscillation parameters.


Physics Letters B | 2013

Lepton Mixing Patterns from a Scan of Finite Discrete Groups

Martin Holthausen; Kher Sham Lim; Manfred Lindner

Abstract The recent discovery of a non-zero value of the mixing angle θ 13 has ruled out tri-bimaximal mixing as the correct lepton mixing pattern generated by some discrete flavor symmetry (barring large next-to-leading order corrections in concrete models). In this work we assume that neutrinos are Majorana particles and perform a general scan of all finite discrete groups with order less than 1536 to obtain their predictions for lepton mixing angles. To our surprise, the scan of over one million groups only yields 3 interesting groups that give lepton mixing patterns which lie within 3-sigma of the current best global fit values. A systematic way to categorize such groups and the implications for flavor symmetry are discussed.


Journal of High Energy Physics | 2013

Electroweak and Conformal Symmetry Breaking by a Strongly Coupled Hidden Sector

Martin Holthausen; Jisuke Kubo; Kher Sham Lim; Manfred Lindner

A bstractThe LHC and other experiments show so far no sign of new physics and long-held beliefs about naturalness should be critically reexamined. We discuss therefore in this paper a model with a combined breaking of conformal and electroweak symmetry by a strongly coupled hidden sector. Even though the conformal symmetry is anomalous, this may still provide an explanation of the smallness of electroweak scale compared to the Planck scale. Specifically we start from a classically conformal model, in which a strongly coupled hidden sector undergoes spontaneous chiral symmetry breaking. A coupling via a real scalar field transmits the breaking scale to the Standard Model Higgs and triggers electroweak symmetry breaking. The model contains dark matter candidates in the form of dark pions, whose stability is being guaranteed by the flavor symmetry of hidden quark sector. We study its relic abundance and direct detection prospects with the Nambu-Jona-Lasinio method and discuss the phase transition in the dark sector as well as in the electroweak sector.


Physical Review D | 2010

Radiative symmetry breaking of the minimal left-right symmetric model

Martin Holthausen; Manfred Lindner; Michael A. Schmidt

Under the assumption of classical conformal invariance, we study the Coleman-Weinberg symmetry breaking mechanism in the minimal left-right symmetric model. This model is attractive as it provides a natural framework for small neutrino masses and the restoration of parity as a good symmetry of nature. We find that, in a large fraction of the parameter space, the parity symmetry is maximally broken by quantum corrections in the Coleman-Weinberg potential, which are a consequence of the conformal anomaly. As the left-right symmetry breaking scale is connected to the Planck scale through the logarithmic running of the dimensionless couplings of the scalar potential, a large separation of the two scales can be dynamically generated. The symmetry breaking dynamics of the model was studied using a renormalization group analysis. Electroweak symmetry breaking is triggered by the breakdown of left-right symmetry, and the left-right breaking scale is therefore expected in the few-TeV range. The phenomenological implications of the symmetry breaking mechanism are discussed.


Physical Review D | 2013

Quark and Leptonic Mixing Patterns from the Breakdown of a Common Discrete Flavor Symmetry

Martin Holthausen; Kher Sham Lim

Assuming the Majorana nature of neutrinos, we recently performed a scan of leptonic mixing patterns derived from finite discrete groups of order less than 1536. Here we show that the 3 groups identified there as giving predictions close to experiment, also contain another class of abelian subgroups that predict an interesting leading order quark mixing pattern where only the Cabibbo angle is generated at leading order. We further broaden our study by assuming that neutrinos are Dirac particles and find 4 groups of order up to 200 that can predict acceptable quark and leptonic mixing angles. Since large flavor groups allow for a multitude of leading order mixing patterns, we define a measure that is suitable to compare the predictivity of a given flavor group taking this fact into account. We give the result of this measure for a wide range of discrete flavor groups and identify the group (Z_18 \times Z_6) \rtimes S_3 as being most predictive in the sense of this measure. We further discuss alternative measures and their implications.


Nuclear Physics | 2013

Solving the Strong CP Problem with Discrete Symmetries and the Right Unitarity Triangle

Stefan Antusch; Martin Holthausen; Michael A. Schmidt; Martin Spinrath

We present a solution to the strong CP problem based on spontaneous CP violation and discrete family symmetries. The model predicts in a natural way the almost right-angled quark unitarity triangle angle ( ’ 90 ) by making the entries of the quark mass matrices either real or imaginary. By this choice the determinants of the mass matrices are rendered real and hence the strong CP phase vanishes. We present a toy model for the quark sector that demonstrates the viability of our approach.


Physical Review D | 2013

Lepton flavor at the electroweak scale: A complete A4 model

Martin Holthausen; Manfred Lindner; Michael A. Schmidt

Apparent regularities in fermion masses and mixings are often associated with physics at a high flavor scale, especially in the context of discrete flavor symmetries. One of the main reasons for that is that the correct vacuum alignment requires usually some high scale mechanism to be phenomenologically acceptable. Contrary to this expectation, we present in this paper a renormalizable radiative neutrino mass model with an A4 flavor symmetry in the lepton sector, which is broken at the electroweak scale. For that we use a novel way to achieve the VEV alignment via an extended symmetry in the flavon potential proposed before by two of the authors. We discuss various phenomenological consequences for the lepton sector and show how the remnants of the flavor symmetry suppress large lepton flavor violating processes. The model naturally includes a dark matter candidate, whose phenomenology we outline. Finally, we sketch possible extensions to the quark sector and discuss its implications for the LHC, especially how an enhanced diphoton rate for the resonance at 125 GeV can be explained within this model.


Journal of High Energy Physics | 2012

Natural vacuum alignment from group theory: the minimal case

Martin Holthausen; Michael A. Schmidt

A bstractDiscrete flavour symmetries have been proven successful in explaining the leptonic flavour structure. To account for the observed mixing pattern, the flavour symmetry has to be broken to different subgroups in the charged and neutral lepton sector. However, cross-couplings via non-trivial contractions in the scalar potential force the group to break to the same subgroup. We present a solution to this problem by extending the flavour group in such a way that it preserves the flavour structure, but leads to an ’accidental’ symmetry in the flavon potential.We have searched for symmetry groups up to order 1000, which forbid all dangerous cross-couplings and extend one of the interesting groups A4, T7, S4, T′ or Δ(27). We have found a number of candidate groups and present a model based on one of the smallest extensions of A4, namely


Physics Letters B | 2010

GIMPs from Extra Dimensions

Martin Holthausen; Ryo Takahashi

{{Q}_8} \rtimes {{A}_4}

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Martin Spinrath

Karlsruhe Institute of Technology

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