Electroweak Symmetry Breaking via QCD

We propose a new mechanism to generate the electroweak scale within the framework of QCD, which is extended to include conformally invariant scalar degrees of freedom belonging to a larger irreducible representation of $SU(3)_c$. The electroweak symmetry breaking is triggered dynamically via the Higgs portal by the condensation of the colored scalar field around 1 TeV. The mass of the colored boson is restricted to be 350 GeV $\lesssim m_S\lesssim$ 3 TeV, with the upper bound obtained from perturbative renormalization group evolution. This implies that the colored boson can be produced at LHC. If the colored boson is electrically charged, the branching fraction of the Higgs decaying into two photons can slightly increase, and moreover, it can be produced at future linear colliders. Our idea of non-perturbative EW scale generation can serve as a new starting point for more realistic model building in solving the hierarchy problem.Comment: 5 pages, 3 figures. Title changed, references added, matches version published in PR

Gamma-ray Line from Nambu-Goldstone Dark Matter in a Scale Invariant Extension of the Standard Model

A recently proposed scale invariant extension of the standard model is modified such that it includes a Dark Matter candidate which can annihilate into gamma-rays. For that a non-zero $U(1)_Y$ hypercharge $Q$ is assigned to the fermions in a QCD-like hidden sector. The Nambu-Goldstone bosons, that arise due to dynamical chiral symmetry breaking in the hidden sector, are cold Dark Matter candidates, and the extension allows them to annihilate into two photons, producing a gamma-ray line spectrum. We find that the gamma-ray line energy must be between 0.7 TeV and 0.9 TeV with the velocity-averaged annihilation cross section $10^{-30}\sim 10^{-26}$ cm^3/s for $Q=1/3$. With a non-zero hypercharge $Q$, the hidden sector is no longer completely dark and can be directly probed by collider experiments.Comment: 21 Pages, 8 Figures. Typos corrected, references added, the section about the properties of the dark matter in our model is extended. Result and conclusion unchanged. To appear in JHE

New Aspects Of Scale And Discrete Flavor Symmetry Breaking

The Standard Model (SM) of particle physics is complete with the discovery of the Higgs particle. However the SM cannot be a complete theory of nature as it does not explain the origin of neutrino mass, dark matter (DM), dark energy, matter-antimatter asymmetry and smallness of the strong CP parameter. From theoretical point of view we do not understand the origin of the scale separation between the electroweak (EW) and the Planck scale, and also the flavor puzzle. In this work we will tackle the hierarchy problem with scale symmetry and the flavor puzzle with discrete flavor symmetries, charting new symmetry groups and their breaking, while investigating their implied phenomenologies along the way. In the first part we provide two novel mechanisms to explain the origin of the EW scale generated by quantum effects from an anomalous breaking of a classical scale invariant extension of the SM. For the first model we utilize a direct scale transmission from condensation of a scalar, charged under a high representation of QCD, to trigger EW symmetry breaking (EWSB) dynamically. In the second model, we will use the indirect scale transmission approach to generate the EW scale transmitted by a singlet scalar mediator which couples to the SM and a strongly coupled hidden sector. Chiral symmetry in the dark fermion sector is broken spontaneously due to nonperturbative effects of the running coupling in the hidden sector, triggering indirectly EWSB due to dimensional transmutation and providing stable DM candidates in the form of dark pions. In the last part of this work we focus on charting new discrete flavor symmetry groups to obtain experimentally acceptable leptonic and quark mixing patterns. The interesting new discrete groups that we have found are classified mathematically and provide a new starting point for model building in discrete flavor symmetr

Quark and leptonic mixing patterns from the breakdown of a common discrete flavor symmetry, Phys

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 (Z18 × Z6) S3 as being most predictive in the sense of this measure. We further discuss alternative measures and their implications

Planck Scale Boundary Conditions and the Higgs Mass

If the LHC does only find a Higgs boson in the low mass region and no other new physics, then one should reconsider scenarios where the Standard Model with three right-handed neutrinos is valid up to Planck scale. We assume in this spirit that the Standard Model couplings are remnants of quantum gravity which implies certain generic boundary conditions for the Higgs quartic coupling at Planck scale. This leads to Higgs mass predictions at the electroweak scale via renormalization group equations. We find that several physically well motivated conditions yield a range of Higgs masses from 127-142 GeV. We also argue that a random quartic Higgs coupling at the Planck scale favors M_H > 150 GeV, which is clearly excluded. We discuss also the prospects for differentiating different boundary conditions imposed for \lambda(M_{pl}) at the LHC. A striking example is M_H = 127\pm 5 GeV corresponding to \lambda(M_{pl})=0, which would imply that the quartic Higgs coupling at the electroweak scale is entirely radiatively generated.Comment: 12 pages, 5 figures; references added and other minor improvements, matches version published in JHE