Neutrino masses from low scale partial compositeness

We consider a class of models in which the neutrinos acquire Majorana masses through mixing with singlet neutrinos that emerge as composite states of a strongly coupled hidden sector. In this framework, the light neutrinos are partially composite particles that obtain their masses through the inverse seesaw mechanism. We focus on the scenario in which the strong dynamics is approximately conformal in the ultraviolet, and the compositeness scale lies at or below the weak scale. The small parameters in the Lagrangian necessary to realize the observed neutrino masses can naturally arise as a consequence of the scaling dimensions of operators in the conformal field theory. We show that this class of models has interesting implications for a wide variety of experiments, including colliders and beam dumps, searches for lepton flavor violation and neutrinoless double beta decay, and cosmological observations. At colliders and beam dumps, this scenario can give rise to striking signals involving multiple displaced vertices. The exchange of hidden sector states can lead to observable rates for flavor violating processes such as μ → eγ and μ → e conversion. If the compositeness scale lies at or below a hundred MeV, the rate for neutrinoless double beta decay is suppressed by form factors and may be reduced by an order of magnitude or more. The late decays of relic singlet neutrinos can give rise to spectral distortions in the cosmic microwave background that are large enough to be observed in future experiments.

Matrix Method for Buckling Analysis of Partially Composite Layered Columns Based on Hencky Bar-Chain Model

The buckling behavior of partially composite layered columns (PCLCs) under axial compressive load is significantly influenced by the slip at the interface of load carrying layers, which brings complexity to the analysis. In this paper, a matrix method based on the Hencky bar-chain model (HBM) is developed for the buckling analysis of PCLCs. The conventional assumption of HBM is modified to consider the interfacial slip properly. Three illustrative problems are presented to show the solving procedure of the HBM-based matrix method. The results are compared to those obtained through analytical formula or finite element method (FEM), and the applicability of the developed method in the buckling analysis of PCLCs with various sectional compositions and boundary conditions is validated. It is proved that the buckling load can be predicted accurately by the developed method. The method is easy to handle, highly adaptable and widely applicable, thus is a promising tool for the buckling analysis of PCLCs.