Title: Effective theory calculation of resonant high-energy scattering Show Chinese title

Title: 共振高能散射的有效理论计算

Abstract: Tests of the standard model and its hypothetical extensions require precise theoretical predictions for processes involving massive, unstable particles. It is well-known that ordinary weak-coupling perturbation theory breaks down due to intermediate singular propagators. Various pragmatic approaches have been developed to deal with this difficulty. In this paper we construct an effective field theory for resonant processes utilizing the hierarchy of scales between the mass of the unstable particle, M, and its width, Gamma. The effective theory allows calculations to be systematically arranged into a series in g^2 and Gamma/M, and preserves gauge invariance in every step. We demonstrate the applicability of this method by calculating explicitly the inclusive line shape of a scalar resonance in an abelian gauge-Yukawa model at next-to-leading order in Gamma/M and the weak couplings. We also discuss the extension to next-to-next-to-leading order and compute an interesting subset of these corrections. Show Chinese abstract

Abstract: 标准模型及其假设扩展的测试需要对涉及大质量、不稳定粒子的过程进行精确的理论预测。 众所周知，由于中间奇异传播子的存在，普通的弱耦合微扰理论会失效。 已经开发出各种实用的方法来处理这个困难。 在本文中，我们利用不稳定粒子的质量M与其宽度Gamma之间的尺度层次，构建了一个用于共振过程的有效场论。 有效理论允许将计算系统地排列成g^2和Gamma/M的级数，并在每一步都保持规范不变性。 我们通过显式计算一个阿贝尔规范-杨-米尔斯模型中标量共振的包含线形，在Gamma/M和弱耦合的次领头阶进行验证，展示了该方法的适用性。 我们还讨论了向次次领头阶的扩展，并计算了这些修正的一个有趣子集。