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arXiv 1107.4060hep-ph
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W袋附近的标准模型CP破坏能解释宇宙学重子不对称性吗?

Can the Standard Model CP violation near the W-bags explain the cosmological baryonic asymmetry?

Yannis Burnier, Edward Shuryak

摘要:

在冷电弱重子生成的情况下,希格斯场的振荡导致不间断相位的亚稳域,希格斯场几乎消失。这些结构域也可以用$W-t-\bar{t}$袋来识别,这是一种由大量($\sim 1000$)规范量子和重(顶夸克和反顶夸克)夸克组成的非拓扑孤子。正如实时数值研究所显示的,sphalerons(违反重子数的拓扑跃迁事件)只发生在这些袋子里。在这项工作中,我们估计的CP破坏量在这种情况下来自标准模型,通过Cabibbo-Kobayashi-Maskawa(CKM)夸克混合矩阵,导致在顶部减去反顶部的差异的人口袋。由于这些顶/反顶是由sphaleron“回收”的,这种人口差异直接导致了宇宙的重子不对称性。我们看看在弱$W$图描述不同的夸克味贡献的干扰中出现在第四阶的效果。我们发现,在与味道有关的相位上,只有在六阶展开时,才出现多个图的取消和明显的符号确定效应。然后,我们估计这些图中发生的弱相互作用的贡献(i)内,(ii)附近和(iii)远离$W-t-\bar{t}$ b袋,优化他们每个人的贡献。我们的结论是,第二(“近”)的情况下是占主导地位的,产生CP破坏的顺序$10^{-10}$,在我们的粗略估计。再加上之前在这种情况下证明的大约为$10^{-2}$的重子破坏率,它使由此产生的不对称性接近于解释宇宙中观察到的重子不对称性所需的值。我们的答案也有一个明确的符号,这似乎是正确的。

英文摘要:

In the scenario of cold electroweak baryogenesis, oscillations of the Higgs field lead to metastable domains of unbroken phase where the Higgs field nearly vanishes. Those domains have also been identified with the $W-t-\bar{t}$ bags, a non-topological soliton made of large number ($\sim 1000$) of gauge quanta and heavy (top and anti-top) quarks. As real-time numerical studies had shown, sphalerons (topological transition events violating the baryon number) occur only inside those bags. In this work we estimate the amount of CP violation in this scenario coming from the Standard Model, via the Cabibbo-Kobayashi-Maskawa (CKM) quark mixing matrix, resulting in top-minus-antitop difference of the population in the bags. Since these tops/anti-tops are "recycled" by sphalerons, this population difference leads directly to the baryonic asymmetry of the Universe. We look at the effect appearing in the 4th order in weak $W$ diagrams describing interference of different quark flavor contributions. We found that there are multiple cancellations of diagrams and clearly sign-definite effect appears only in the 6th order expansion over flavor-dependent phases. We then estimate contributions to these diagrams in which weak interaction occurs (i) inside, (ii) near and (iii) far from the $W-t-\bar{t}$ b-bags, optimizing the contributions in each of them. We conclude that the second ("near") scenario is the dominant one, producing CP violation of the order of $10^{-10}$, in our crude estimates. Together with the baryon violation rate of about $10^{-2}$, previously demonstrated for this scenario, it puts the resulting asymmetry close to what is needed to explain the observed baryonic asymmetry in the Universe. Our answer also has a definite sign, which apparently seems to be the correct one.

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