标题： 在轻子对撞机上对正性进行无歧义的检验 显示英文标题

标题： An unambiguous test of positivity at lepton colliders

摘要： 轻子对撞机的双光子通道，$e^+e^- (\mu^+\mu^-) \to \gamma \gamma$，具有一个显著特征，即主要的新物理贡献仅来自八维算符。 这一贡献受到一组正定性界限的约束，这些界限来源于量子场论的基本原理，如幺正性、局域性和解析性。 因此，这些正定性界限适用于最直接的可观测量——双光子截面。 这一独特特性提供了对这些原理的清晰、稳健且无歧义的检验。 我们估计了各种未来轻子对撞机在探测该通道中的八维算符以及测试正定性界限的能力。 我们表明，正定性界限可以消除某些有效算符之间的简并，并显著改变全局分析的视角。 我们还对高能极限下的$\gamma\gamma/Z\gamma/ZZ$过程进行了综合分析，并指出了它们之间的重要相互作用。 显示英文摘要

摘要： The diphoton channel at lepton colliders, $e^+e^- (\mu^+\mu^-) \to \gamma \gamma$, has a remarkable feature that the leading new physics contribution comes only from dimension-eight operators. This contribution is subject to a set of positivity bounds, derived from fundamental principles of Quantum Field Theory, such as unitarity, locality and analyticity. These positivity bounds are thus applicable to the most direct observable -- the diphoton cross sections. This unique feature provides a clear, robust, and unambiguous test of these principles. We estimate the capability of various future lepton colliders in probing the dimension-eight operators and testing the positivity bounds in this channel. We show that positivity bounds can lift certain degeneracies among the effective operators and significantly change the perspectives of a global analysis. We also perform a combined analysis of the $\gamma\gamma/Z\gamma/ZZ$ processes in the high energy limit and point out the important interplay among them.