Surabhi Srivastava | Search arXiv

arXiv2026

Escaping Solar Capture: Majoron mediated Elastic Dark Matter for the LZ 248~keV Event

We interpret the $248~\mathrm{keV_{nr}}$ nuclear-recoil candidate reported by LZ through elastic dark matter scattering mediated by a light Majoron. The Majoron provides a natural origin for the required pseudoscalar interaction: it is the pseudo Nambu-Goldstone boson associated with spontaneous lepton number breaking, directly connecting the recoil signal to neutrino mass generation. After a model independent analysis of this idea, we present a concrete realization in a scotogenic ultraviolet completion in which the lightest singlet Majorana fermion is dark matter and acquires both its mass and Majoron coupling from the symmetry breaking dynamics. A vector like up type quark and a type-I Dirac seesaw in quark sector communicate the Majoron interaction to the up quark. At low energies, the resulting portal generates the nonrelativistic operator $\mathcal O_6$, whose momentum dependence reproduces the high-recoil event without overpopulating the lower energy bins. Its spin structure removes the dominant heavy element solar capture channels, while capture on hydrogen is suppressed by poor kinematic matching and small momentum transfer. This construction simultaneously reproduces the LZ recoil spectrum and the observed thermal relic abundance while strongly suppressing solar capture.

hep-ph↗

arXiv2024

Combined concurrent Physical and Chemical model for accelerated weathering damages of polyurethane-based coatings

Paints and coatings undergo a variety of physical and chemical changes under environmental exposures. Accurate prediction of these changes is important for the applications of coatings. This work presents a novel approach to modeling accelerated weathering of coating by combining concurrent physical and chemical processes. The model integrates key factors influencing coating degradation and employs a multi-scale framework to capture macro-scale physical changes and micro-level chemical transformations. The chemical component/model simulates photo-degradation reactions using kinetic equations, while the physical component uses Monte Carlo simulations where repeated random events develop surface erosion. The surface topography and chemistry of coating is generated statistically through the physical model. The variations in surface topography and chemistry of coating are correlated with the chemical changes from the chemical model, resulting in estimation of both physical and chemical changes in the coating during real accelerated weathering time. Results demonstrate accurate predictions of chemistry changes, surface degradation profiles, roughness, gloss loss, and relative fracture toughness, which are validated successfully with the experimentally available data. This integrated approach provides insight into coating failure mechanisms, enabling accurate service life prediction, and serve as a tool for formulating durable coatings and optimizing testing protocols.

cond-mat.soft↗