Title: Constraining screened fifth forces with the electron magnetic moment Show Chinese title

Title: 用电子磁矩限制屏蔽的第五种力

Abstract: Chameleon and symmetron theories serve as archetypal models for how light scalar fields can couple to matter with gravitational strength or greater, yet evade the stringent constraints from classical tests of gravity on Earth and in the Solar System. In this work, we investigate how a precision measurement of the electron magnetic moment places meaningful constraints on both chameleons and symmetrons. Two effects are identified: First, virtual chameleons and symmetrons run in loops to generate quantum corrections to the intrinsic value of the magnetic moment; a common process widely considered in the literature for many scenarios beyond the Standard Model. A second effect, however, is unique to scalar fields that exhibit screening. A scalar bubblelike profile forms inside the experimental vacuum chamber and exerts a fifth force on the electron, leading to a systematic shift in the experimental measurement. In quantifying this latter effect, we present a novel approach that combines analytic arguments and a small number of numerical simulations to solve for the bubblelike profile quickly for a large range of model parameters. Taken together, both effects yield interesting constraints in complementary regions of parameter space. While the constraints we obtain for the chameleon are largely uncompetitive with those in the existing literature, this still represents the tightest constraint achievable yet from an experiment not originally designed to search for fifth forces. We break more ground with the symmetron, for which our results exclude a large and previously unexplored region of parameter space. Central to this achievement are the quantum correction terms, which are able to constrain symmetrons with masses in the range $\mu \in [10^{-3.88},10^8]\,\text{eV}$, whereas other experiments have hitherto only been sensitive to 1 or 2 orders of magnitude at a time. Show Chinese abstract

Abstract: 变色龙理论和对称子理论作为典型模型，展示了轻标量场如何以引力强度或更强的耦合方式与物质相互作用，同时又能避开地球和太阳系中经典引力测试所施加的严格限制。 在这项工作中，我们研究了电子磁矩的精确测量如何对变色龙和对称子施加有意义的约束。 识别出两种效应：首先，虚拟的变色龙和对称子在环路中运行，生成对磁矩固有值的量子修正；这是文献中广泛考虑的许多超出标准模型情景中的常见过程。 然而，第二种效应则独特地出现在表现出屏蔽特性的标量场中。在实验真空室内部形成一个类似气泡的分布，并对电子施加第五种力，导致实验测量出现系统性偏移。 为了量化后一种效应，我们提出了一种新颖的方法，结合解析论证和少量数值模拟，快速求解大范围模型参数下的气泡状分布。 综合来看，这两种效应在参数空间的互补区域产生了有趣约束。 尽管我们得到的变色龙约束在很大程度上不如现有文献中的约束具有竞争力，但这一成果仍然代表了迄今为止从原本未设计用于搜索第五种力的实验所能达到的最严格约束。 我们在对称子方面取得了更大的进展，我们的结果排除了一个之前未被探索的大范围参数空间。 这一成就的核心在于量子修正项，它能够约束质量范围在$\mu \in [10^{-3.88},10^8]\,\text{eV}$的对称子，而其他实验迄今为止只能一次敏感到 1 或 2 个数量级的变化。