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Fowlie A.,Estonian National Institute of Chemical Physics and Biophysics | Marzola L.,University of Tartu
Nuclear Physics B | Year: 2014

Motivated by a hint in a CMS search for right-handed W-bosons in eejj final states, we propose an experimental test of quark-mixing matrices in a general left-right symmetric model, based on counting the numbers of b-tags from right-handed W-boson hadronic decays. We find that, with our test, differences between left- and right-handed quark-mixing matrices could be detected at the LHC with s=14 TeV. With an integrated luminosity of about 20/fb, our test is sensitive to right-handed quark-mixing angles as small as about 30° and with 3000/fb, our test's sensitivity improves to right-handed mixing angles as small as about 7.5°. Our test's sensitivity might be further enhanced by tuning b-tagging efficiency against purity. © 2014 The Authors. Source


Hambye T.,Free University of Colombia | Strumia A.,National Institute of Nuclear Physics, Italy | Strumia A.,Estonian National Institute of Chemical Physics and Biophysics
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

Assuming that naturalness should be modified by ignoring quadratic divergences, we propose a simple extension of the standard model where the weak scale is dynamically generated together with an automatically stable vector. Identifying it as thermal dark matter, the model has one free parameter. It predicts one extra scalar, detectable at colliders, which triggers a first-order dark/electroweak cosmological phase transition with production of gravitational waves. Vacuum stability holds up to the Planck scale. © 2013 American Physical Society. Source


Kannike K.,Normal School of Pisa | Kannike K.,Estonian National Institute of Chemical Physics and Biophysics
European Physical Journal C | Year: 2012

A scalar potential of the form λ ab φ a 2φ a 2 is bounded from below if its matrix of quartic couplings λ ab is copositive-positive on non-negative vectors. Scalar potentials of this form occur naturally for scalar dark matter stabilised by a ℤ 2 symmetry. Copositivity criteria allow us to derive analytic necessary and sufficient vacuum stability conditions for the matrix λ ab. We review the basic properties of copositive matrices and analytic criteria for copositivity. To illustrate these, we re-derive the vacuum stability conditions for the inert doublet model in a simple way, and derive the vacuum stability conditions for the ℤ 2 complex singlet dark matter, and for the model with both a complex singlet and an inert doublet invariant under a global U(1) symmetry. © 2012 Springer-Verlag / Società Italiana di Fisica. Source


Fowlie A.,Estonian National Institute of Chemical Physics and Biophysics
European Physical Journal C | Year: 2014

With Bayesian statistics, we investigate the full parameter space of the constrained “next-to-minimal” supersymmetric standard model (CNMSSM) with naturalness priors, which were derived in a previous work. In the past, most Bayesian analyses of the CNMSSM ignored naturalness of the electroweak (EW) scale by making prejudicial assumptions for parameters defined at the EW scale. We test the CNMSSM against the CMSSM with Bayesian evidence, which, with naturalness priors, incorporates a penalty for fine-tuning of the EW scale. With the evidence, we measure credibility with respect to all measurements, including the EW scale and LHC direct searches. We find that the evidence in favor of the CNMSSM versus the CMSSM is “positive” to “strong” but that if one ignores the (Formula presented.)-problem, the evidence is “barely worth mentioning” to “positive”. The (Formula presented.)-problem significantly influences our findings. Unless one considers the (Formula presented.)-problem, the evidence in favor of the CNMSSM versus the CMSSM is at best “positive”, which is two grades below “very strong”. We, furthermore, identify the most probable regions of the CMSSM and CNMSSM parameter spaces and examine prospects for future discovery at hadron colliders. © 2014, The Author(s). Source


Hektor A.,Estonian National Institute of Chemical Physics and Biophysics | Marzola L.,University of Tartu
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2014

Coy dark matter removes the tension between the traditional WIMP paradigm of dark matter and the latest exclusion bounds from direct detection experiments. In this paper we present a leptophilic coy dark matter model that, on top of explaining the spatially extended 1-5 GeV γ-ray excess detected at the galactic center, reconciles the measured anomalous magnetic moment of muon with the corresponding standard model prediction. The annihilation channel of dark matter is χχ→ττ¯ with the dark matter mass mχ=9.43(-0.52+.063stat)(±1.2sys)GeV given by best-fit of the γ-ray excess. Fitting the measured anomalous magnetic moment of the muon requires instead a pseudoscalar mediator with a minimal mass ma=12-3+7GeV. © 2014 American Physical Society. Source

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