We discuss first-order electroweak phase transition in models with extended Higgs sectors for the case with relatively heavy additional scalar bosons. We first show that, by the combination of the sphaleron decoupling condition, perturbative unitarity, and vacuum stability, mass upper bounds on additional scalar bosons can be obtained at the TeV scale even at the alignment limit where the lightest Higgs boson behaves exactly like the SM Higgs boson at tree level. We then discuss phenomenological impacts of the case with the additional scalar bosons with the mass near 1 TeV. Even when they are too heavy to be directly detected at current and future experiments at hadron colliders, the large deviation in the triple Higgs boson coupling can be a signature for first-order phase transition due to quantum effects of such heavy additional Higgs bosons. On the other hand, gravitational waves from the first-order phase transition are found to be weaker in this case as compared to that with lower masses of additional scalar bosons.

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由相对重的附加希格斯玻色子产生的强一阶电弱相变

对于具有相对重的附加标量玻色子的情况，我们讨论了具有扩展希格斯扇区的模型中的一阶电弱相变。我们首先表明，通过将螺旋体解耦条件、微扰单一性和真空稳定性相结合，即使在最轻的希格斯玻色子行为与 SM 完全相同的对齐极限下，也可以在 TeV 尺度上获得额外标量玻色子的质量上限树级别的希格斯玻色子。然后，我们讨论带有质量接近 1 TeV 的附加标量玻色子的情况的现象学影响。即使它们太重而无法在当前和未来的强子对撞机实验中直接检测到，由于如此重的额外希格斯玻色子的量子效应，三重希格斯玻色子耦合的巨大偏差可能是一阶相变的标志。