Measurement of the very rare K+→π+ννˉK^+ \to \pi^+ \nu \bar\nu decay

The decay K+→π+νν¯ , with a very precisely predicted branching ratio of less than 10−10 , is among the best processes to reveal indirect effects of new physics. The NA62 experiment at CERN SPS is designed to study the K+→π+νν¯ decay and to measure its branching ratio using a decay-in-flight technique. NA62 took data in 2016, 2017 and 2018, reaching the sensitivity of the Standard Model for the K+→π+νν¯ decay by the analysis of the 2016 and 2017 data, and providing the most precise measurement of the branching ratio to date by the analysis of the 2018 data. This measurement is also used to set limits on BR(K+→π+X ), where X is a scalar or pseudo-scalar particle. The final result of the BR(K+→π+νν¯ ) measurement and its interpretation in terms of the K+→π+X decay from the analysis of the full 2016-2018 data set is presented, and future plans and prospects are reviewed

Multi-Physics of Dynamic Elastic Metamaterials and Earthquake Systems

Microstructured materials, namely metamaterials, are one of the most relevant topics of the recent period due to their interdisciplinary nature. Driven by their wide range of applications, we provide an overview of a class of elastic solids which embed dynamic microstructures capable of trapping energy when subject to dynamic loads. Based on the recently developed modeling approaches, we show several applications related to wave cloaking, filtering and also multi-structured surfaces, often referred to as meta-surfaces. These culminate in the analysis of a practical example, based on a real-life recent seismic event induced by a hydrofracture exploration. The latter shows the viability of the vibration analysis in the assessment of the seismic response, and also the role of meta-surfaces as localisers of vibrations, e.g. suggesting non-periodic earthquake tolerant design strategies of housing estates.</jats:p