Reinterpreting the ATLAS bounds on heavy neutral leptons in a realistic neutrino oscillation model

Heavy neutral leptons (HNLs) are hypothetical particles, motivated in the first place by their ability to explain neutrino oscillations. Experimental searches for HNLs are typically conducted under the assumption of a single HNL mixing with a single neutrino flavor. However, the resulting exclusion limits may not directly constrain the corresponding mixing angles in realistic HNL models — those which can explain neutrino oscillations. The reinterpretation of the results of these experimental searches turns out to be a non-trivial task, that requires significant knowledge of the details of the experiment. In this work, we perform a reinterpretation of the latest ATLAS search for HNLs decaying promptly to a tri-lepton final state. We show that in a realistic model with two HNLs, the actual limits can vary by several orders of magnitude depending on the free parameters of the model. Marginalizing over the unknown model parameters leads to an exclusion limit on the total mixing angle which can be up to 3 orders of magnitude weaker than the limits reported in ref. [1]. This demonstrates that the reinterpretation of results from experimental searches is a necessary step to obtain meaningful limits on realistic models. We detail a few steps that can be taken by experimental collaborations in order to simplify the reuse of their results.

Improving the Four-Dimensional Incremental Analysis Update (4DIAU) with the HWRF 4DEnVar Data Assimilation System for Rapidly Evolving Hurricane Prediction

Short-term spin-up for strong storms is a known difficulty for the operational Hurricane Weather Research and Forecasting (HWRF) model after assimilating high-resolution inner-core observations. Our previous study associated this short-term intensity prediction issue with the incompatibility between the HWRF model and the data assimilation (DA) analysis. While improving physics and resolution of the model was found helpful, this study focuses on further improving the intensity predictions through the four-dimensional incremental analysis update (4DIAU).In the traditional 4DIAU, increments are pre-determined by subtracting background forecasts from analyses. Such pre-determined increments implicitly require linear evolution assumption during the update, which are hardly valid for rapid-evolving hurricanes. To confirm the hypothesis, a corresponding 4D analysis nudging (4DAN) method which uses online increments is first compared with the 4DIAU in an oscillation model. Then, variants of 4DIAU are proposed to improve its application for nonlinear systems. Next, 4DIAU, 4DAN and their proposed improvements are implemented into the HWRF 4DEnVar DA system and are investigated with hurricane Patricia (2015).Results from both oscillation model and HWRF model show that: 1. the pre-determined increments in 4DIAU can be detrimental when there are discrepancies between the updated and background forecasts during a nonlinear evolution. 2. 4DAN can improve the performance of incremental update upon 4DIAU, but its improvements are limited by the over-filtering. 3. Relocating initial background before the incremental update can improve the corresponding traditional methods. 4. the feature-relative 4DIAU method improves the incremental update the most and produces the best track and intensity predictions for Patricia among all experiments.

DEFINING PARAMETERS FOR THE OSCILLATION MODEL OF LOAD FLOW OF GLOBAL ACTIVITIES IN A FULLY DISTRIBUTED EXASCALE SYSTEM

Distributed exascale computing systems are the idea of the HPC systems, that capable to perform one exaflop operations per second in dynamic and interactive nature without central managers. In such environment, each node should manage its own load itself and it should be found the basic rules of load distribution for all nodes because of being able to optimize the load distribution without central managers. In this paper proposed oscillation model for load distribution in fully distributed exascale systems and defined some parameters for this model and mentioned about feature works.

An undamped oscillation model with two different contact angles for a spherical droplet impacting on solid surface

Предложен нелинейный подход описания колебания сферической капли на твердой поверхности. Интегрирование уравнений движений осуществляется без использования линеаризации тригонометрических функций, зависящих от угла контакта. Иными словами, угол контакта является произвольной конечной величиной. Проведено исследование влияние силы тяжести на угол контакта и радиус распространения капли по твердой поверхности. Таким образом, было найдено нелинейное уравнение, описывающее изменение радиуса распространения капли в зависимости от времени. Данное уравнение было численно проинтегрировано. Исследование численной сходимости осуществлялось посредством сравнения с известными модельными точными решениями и известными экспериментальными данными. На основании исследования методами численного интегрирования полученного в статье уравнения можно сделать вывод о целесообразности использования математической модели для описания и исследования новых физических эффектов при колебании капель.