多体衰变分析--一个新的介子-介子子振幅唯象模型
Multibody decay analyses -- a new phenomenological model for meson-meson subamplitudes
摘要：
介子-介子振幅本身就很重要，在重介子和τ衰变的分析中也起着关键作用。在这项工作中，我们提出了一个新的唯象模型，适用于所有的$SU(3)$介子两体末态相互作用的能量约为2 GeV。它的目的是取代那些进入旧的等压线模型，产生于20世纪60年代，早在QCD的发展。我们的新建议和等压线模型中使用的振幅之间的唯一相似之处是弹性区域中的矢量共振。在其他情况下，特别是那些涉及标量共振和耦合通道，等压线模型是不兼容的后QCD动力学。为了令人信服地支持这些主张，并激励我们的方法，我们认为应用程序的$ππ$振幅和比较我们的版本与等压线模型在几个不同的情况下。我们还表明，新的模型提供了一个明确的机制，负责急剧上升观察到的$ππ$相位周围$1\,$ GeV。这里提出的唯象振幅适用于给定通道中的任何数量的共振，并且仅依赖于质量和耦合常数作为自由参数。关于理论，它们在低能量下结合了手征对称性，包括耦合通道，并在适当时尊重幺正性。
英文摘要：
Meson-meson amplitudes are important on their own and also play key roles in analyses of heavy-meson and tau decays. In this work we propose a new phenomenological model suited to all $SU(3)$ mesonic two-body final state interactions up to energies around 2 GeV. It is aimed at replacing those entering the old isobar model, produced in the 1960's, long before the development of QCD. The only similarity between our new proposal and amplitudes used in the isobar model concern vector resonances in the elastic regime. In other situations, especially those involving scalar resonances and coupled channels, the isobar model is not compatible with post-QCD dynamics. In order to support these claims convincingly and to motivate our approach, we consider applications to the $ππ$ amplitude and compare our version with the isobar model in several different instances. We also show that the new model provides a clear indication of the mechanism responsible for the sharp rise observed in the $ππ$ phase around $1\,$ GeV. The phenomenological amplitudes proposed here are suited to any number of resonances in a given channel and rely just on masses and coupling constants as free parameters. Concerning theory, they incorporate chiral symmetry at low energies, include coupled channels and respect unitarity whenever appropriate.
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