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首页> 外文期刊>Physical review, D >What if the masses of the first two quark families are not generated by the standard model Higgs boson?
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What if the masses of the first two quark families are not generated by the standard model Higgs boson?

机译：如果前两个夸克族的质量不是由标准模型希格斯玻色子产生的，该怎么办？

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We point out that in the standard model there is meaningful quark mixing even in the extreme chiral (EC) limit, where only the third generation of quarks acquires mass. This mixing is in general expected to be of order 1 and the fact that | V 13 | 2 + | V 23 | 2 ≈ 1.6 × 1 0 ? 3 implies a novel fine-tuning problem in the SM which we point out for the first time. We propose a possible way of avoiding this fine-tuning by introducing a symmetry S which leads to V CKM = 1 , with only the third generation of quarks acquiring mass. We consider two scenarios for generating the mass of the first two quark generations and full quark mixing based on the assumption that the masses of the first two quark families are not generated by the standard Higgs. One consists of the introduction of a second Higgs doublet which is neutral under S . The second scenario consists of assuming new physics at a high energy scale, contributing to the masses of light quark generations, in an effective field theory approach. This last scenario leads to couplings of the Higgs particle to s s ˉ and c c ˉ which are significantly enhanced with respect to those of the SM. In both schemes, one has scalar-mediated flavor-changing neutral currents which are naturally suppressed. Flavor-violating top decays are predicted in the second scenario at the level Br ( t → h c ) ≥ 5 × 1 0 ? 5 .
机译：我们指出，在标准模型中，即使在极端手性（EC）极限中也存在有意义的夸克混合，在这种情况下，只有第三代夸克才能获得质量。通常期望这种混合为1阶，并且| V 13 | 2 + | V 23 | 2≈1.6×1 0？图3暗示了SM中的一个新的微调问题，这是我们第一次指出。我们提出了一种可能的方法，即通过引入导致V CKM = 1的对称S来避免这种微调，只有第三代夸克才能获得质量。我们基于两种假设来生成前两个夸克世代的质量和完全夸克混合，这是基于以下假设：前两个夸克族的质量不是由标准希格斯生成的。其中之一是引入第二个希格斯二重态，它在S之下是中性的。第二种情况是采用一种有效的场论方法，假设一个高能级的新物理学，为光夸克的产生做出贡献。最后一种情况导致希格斯粒子与s s和c c coupling的耦合，相对于SM的s significantly和c c coupling显着增强。在这两种方案中，一个都具有自然抑制的标量介导的改变风味的中性电流。在第二种情况下，预测的破坏风味的顶部衰减将在Br（t→h c）≥5×1 0？ 5。

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