FlexibleSUSY extended to automatically compute physical quantities in any beyond the standard model theory: Charged lepton flavor violation processes, Higgs decays, and user-defined observables

FlexibleSUSY is a framework for the automated computation of physical quantities (observables) in models beyond the Standard Model (BSM). This paper describes an extension of FlexibleSUSY which allows to define and add new observables that can be enabled and computed in applicable user-defined BSM models. The extension has already been used to include Charged Lepton Flavor Violation (CLFV) observables, but further observables can now be added straightforwardly. The paper is split into two parts. The first part is non-technical and describes from the user's perspective how to enable the calculation of predefined observables, in particular CLFV observables. The second part of the paper explains how to define new observables such that their automatic computation in any applicable BSM model becomes possible. A key ingredient is the new NPointFunctions extension which allows to use tree-level and loop calculations in the model-independent setup of observables. Three examples of increasing complexity are fully worked out. This illustrates the features and provides code snippets that may be used as a starting point for implementation of further observables.

FlexibleSUSY是一款用于自动计算超出标准模型（Beyond the Standard Model，简称BSM）框架下物理量（可观测量）的软件框架。本文介绍了FlexibleSUSY的一项扩展功能，支持用户自定义并添加新的可观测量，可在适配的用户自定义BSM模型中启用并计算这些可观测量。该扩展已被用于集成带电轻子味破缺（Charged Lepton Flavor Violation，简称CLFV）可观测量，如今还可便捷地添加更多类型的可观测量。本文分为两个部分：第一部分为非技术导向内容，从用户视角介绍如何启用预定义可观测量的计算，尤其是CLFV可观测量的计算流程；第二部分则阐述如何定义新型可观测量，使其可在任意适配的BSM模型中实现自动计算。该扩展的核心组成部分为新型N点函数（NPointFunctions）扩展模块，支持在与模型无关的可观测量搭建流程中使用树级与圈级计算方法。本文完整给出并详细推导了三个复杂度逐级提升的示例，对该扩展的功能进行演示，并提供了可作为后续可观测量实现开发起点的代码片段。