多重宇宙中的阿尔法-阿尔法散射
Alpha-alpha scattering in the Multiverse
摘要：
本文研究了标准模型的基本参数，即轻夸克质量、电磁精细结构常数和QCD θ角变化时低能α-α散射的相移.作为第一步，我们重新计算α-α散射在我们的宇宙中利用各种改进的绝热投影方法，这导致一个改进的，无参数的预测的S-和D-波的相移实验室能量低于10兆电子伏。我们发现，在π介子质量的积极变化有一个小的影响，S波相移，而降低π介子质量增加了一些排斥在两个α系统。对D波相移的影响变得更加明显，如由D波共振参数所表示的。精细结构常数的变化对低能α-α相移几乎没有影响。我们进一步表明，在手征展开中，这些相移相对于QCD θ角的变化可以用θ依赖的π介子质量来表示。
英文摘要：
We investigate the phase shifts of low-energy alpha-alpha scattering under variations of the fundamental parameters of the Standard Model, namely the light quark mass, the electromagnetic fine-structure constant as well as the QCD theta-angle. As a first step, we recalculate alpha-alpha scattering in our Universe utilizing various improvements in the adiabatic projection method, which leads to an improved, parameter-free prediction of the S- and D-wave phase shifts for laboratory energies below 10 MeV. We find that positive shifts in the pion mass have a small effect on the S-wave phase shift, whereas lowering the pion mass adds some repulsion in the two-alpha system. The effect on the D-wave phase shift turns out to be more pronounced as signaled by the D-wave resonance parameters. Variations of the fine-structure constant have almost no effect on the low-energy alpha-alpha phase shifts. We further show that up-to-and-including next-to-leading order in the chiral expansion, variations of these phase shifts with respect to the QCD theta-angle can be expressed in terms of the theta-dependent pion mass.
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