ditop和ditau通道中的LHC过量解释为400- GeV赝标量共振
Interpretation of LHC excesses in ditop and ditau channels as a 400-GeV pseudoscalar resonance
摘要：
自从2012年在大型强子对撞机上发现希格斯玻色子以来，作为粒子物理学标准模型的最后一个缺失部分，人们一直在密集地寻找任何新物理学的线索，迄今为止还没有得到证实。然而，有轻微的偏差，从SM是值得研究的。CMS的合作报告，在寻找质量中心能量为13 TeV、光度为35.9 fb $^{-1}$的$t \bar t$中衰减的重共振时，在3.5 $σ$能级上（在别处寻找效应后为1.9 $σ$）与SM预测的偏差。此外，在由ATLAS协作在$\sqrt{s}=13$ TeV和$\mathcal{L}=139$ fb $^{-1}$上执行的ditau最终状态搜索中，还观察到在2 $σ$水平上偏离SM。有趣的是，这两个轻微的过度都与一个新的质量约为400 GeV的赝标玻色子兼容，至少耦合到第三代费米子和胶子。从一个纯粹的唯象的角度来看，我们检查的可能性，400-GeV的赝标量可以占这些偏差，并在同一时间满足的限制，它提供的贡献，并分析了ATLAS和CMS实验的其余通道。在得到与实验测量一致的有效耦合范围后，我们研究了能产生这种赝标共振的规范不变UV完备，它可以容纳在1 $σ$水平上具有一致性的$SO(6)/SO(5)$模型和2 $σ$水平上的$SO(5)\times U(1)_{P}\times U(1)_{X}/SO(4)\times U(1)_X$中，而在一般的双希格斯偶线模型中，需要非常大的四次耦合来解释它。
英文摘要：
Since the discovery in 2012 of the Higgs boson at the LHC, as the last missing piece of the Standard Model of particle physics, any hint of new physics has been intensively searched for, with no confirmation to date. There are however slight deviations from the SM that are worth investigating. The CMS collaboration has reported, in a search for heavy resonances decaying in $t \bar t$ with a 13-TeV center-of-mass energy and a luminosity of 35.9 fb$^{-1}$, deviations from the SM predictions at the 3.5$σ$ level locally (1.9$σ$ after the look-elsewhere effect). In addition, in the ditau final state search performed by the ATLAS collaboration at $\sqrt{s}=13$ TeV and $\mathcal{L}=139$ fb$^{-1}$, deviations from the SM at the 2$σ$ level have been also observed. Interestingly, both slight excesses are compatible with a new pseudoscalar boson with a mass around 400 GeV that couples at least to fermions of the third generation and gluons. Starting from a purely phenomenological perspective, we inspect the possibility that a 400-GeV pseudoscalar can account for these deviations and at the same time satisfy the constraints on the rest of the channels that it gives contributions to and that are analyzed by the ATLAS and CMS experiments. After obtaining the range of effective couplings compatible with all experimental measurements, we study the gauge invariant UV completions that can give rise to this type of pseudoscalar resonance, which can be accommodated in an $SO(6)/SO(5)$ model with consistency at the 1$σ$ level and in a $SO(5)\times U(1)_{P}\times U(1)_{X}/SO(4)\times U(1)_X$ at the 2$σ$ level, while exceedingly large quartic couplings would be necessary to account for it in a general two Higgs doublet model.
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