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arXiv 1602.00475hep-ph
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750 GeV复合轴子作为LHC双光子共振

750 GeV Composite Axion as the LHC Diphoton Resonance

Neil D. Barrie, Archil Kobakhidze, Matthew Talia, Lei Wu

备注：
10 pages, 3 figures; Minor revision, updated references to be consistent with PLB published version
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摘要：

我们建议，750 GeV的共振，大概观察到在早期的大型强子对撞机运行2的数据，可能是一个沉重的复合轴子，结果从凝聚的一个假设的夸克在一个高的颜色表示的传统QCD。该模型的动机是最近提出的强CP问题的解决方案，是非常经济的，基本上是由额外的夸克的属性-它的色荷，超荷和质量定义的。轴子质量和它与两个光子的耦合（通过轴向异常）可以根据这些参数计算。轴子主要通过光子融合（$γγ\to {\cal A}$）产生，随后是$ Z $载体玻色子融合和在LHC的相关产生。我们发现轴子的总双光子截面可以用观测到的过剩量来拟合。结合对截面的要求，使其再现双光子过剩事件，与总宽度（$Γ_{tot} \leqslant 45$ GeV）的界限，我们得到的有效耦合范围$1.6\times 10^{-4}$ GeV $^{-1}\gtrsim C_{\cal A} \gtrsim 6.5\times 10^{-5}$ GeV $^{-1}$。在允许的耦合的这个窗口内，该模型有利于窄宽度共振和$ y_{Q}^2 \sim \mathcal{O}(10)$。此外，我们观察到，相关的生产$q\bar{q} \to {\cal A}γ\to γγγ$可能会产生相当数量的三光子事件在未来的LHC和$ e^{+} e^{-} $对撞机。然而，稀有衰变$Z\to\mathcal{A}^*γ\to γγγ$被发现太小，无法在大型强子对撞机上探测。

英文摘要：

We propose that the 750 GeV resonance, presumably observed in the early LHC Run 2 data, could be a heavy composite axion that results from condensation of a hypothetical quark in a high-colour representation of conventional QCD. The model, motivated by a recently proposed solution to the strong CP problem, is very economical and is essentially defined by the properties of the additional quark - its colour charge, hypercharge and mass. The axion mass and its coupling to two photons (via axial anomaly) can be computed in terms of these parameters. The axion is predominantly produced via photon fusion ($γγ\to {\cal A}$) which is followed by $ Z $ vector boson fusion and associated production at the LHC. We find that the total diphoton cross section of the axion can be fitted with the observed excess. Combining the requirement on the cross-section, such that it reproduces the diphoton excess events, with the bounds on the total width ($Γ_{tot} \leqslant 45$ GeV), we obtain the effective coupling in the range $1.6\times 10^{-4}$ GeV$^{-1}\gtrsim C_{\cal A} \gtrsim 6.5\times 10^{-5}$ GeV$^{-1}$. Within this window of allowed couplings the model favours a narrow width resonance and $ y_{Q}^2 \sim \mathcal{O}(10)$. In addition, we observe that the associated production $q\bar{q} \to {\cal A}γ\to γγγ$ can potentially produce a sizeable number of three photon events at future LHC and $ e^{+} e^{-} $ colliders. However, the rare decay $Z\to\mathcal{A}^*γ\to γγγ$ is found to be too small to be probed at the LHC.

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