包括在LHC处的非指向光子的超对称多光子信号
Multi-photon signal in supersymmetry comprising non-pointing photon(s) at the LHC
摘要：
我们研究了一个独特的超对称信号的多光子与射流和失踪的横向能量。这些光子中至少有一个的原点在位移顶点，因此延迟和非指向。我们考虑一个超对称的情形，其中引力伴子是最轻的超对称粒子（LSP）（质量为$\sim 1~{keV}$），最轻的中性伴子是次轻的超对称粒子（NLSP）。NLSP在探测器内主要衰变为光子和引力子，衰变长度为$cτ_{\tildeχ}\sim$ 50-100 cm。此外，我们还假设次轻的中性伴子和最轻的中性伴子几乎是简并的，这将导致次轻的中性伴子迅速辐射衰变为光子和具有大分支比的最轻的中性伴子.这种简并中性伴子可以在$SU(5)$、$SO(10)$和$E(6)$大统一理论（GUT）的各种表示中实现。非指向光子可以在ATLAS内探测器的电磁量热器上重建，该电磁量热器具有良好的定时和方向分辨率。我们发现，在积分亮度为100 $fb^{-1}$的质心能量$E_{cm}=14 ~{TeV}$的情况下，除了几千个双光子事件之外，还可以看到LHC中数百个三光子事件和几个四光子事件的证据。我们还预测了LHC运行初期的事件率。
英文摘要：
We study a distinct supersymmetric signal of multi-photons in association with jets and missing transverse energy. At least one of these photons has the origin in displaced vertex, thus delayed and non-pointing. We consider a supersymmetric scenario in which the gravitino is the lightest supersymmetric particle (LSP) (with a mass $\sim 1~{keV}$) and the lightest neutralino is the next-to-lightest supersymmetric particle (NLSP). The NLSP decays dominantly into a photon and a gravitino within the detector with a decay length ranging from $cτ_{\tildeχ}\sim$ 50-100 cm. In addition, we assume that the second lightest neutralino and the lightest neutralino are nearly degenerate and this leads to a prompt radiative decay of the next-to-lightest neutralino into a photon and a lightest neutralino with a large branching ratio. Such degenerate neutralinos can be realised in various representations of the $SU(5)$, $SO(10)$, and $E(6)$ Grand Unified Theories (GUTs). The non-pointing photons can be reconstructed at the electromagnetic calorimeter of the ATLAS inner-detector, which have been designed with good timing and directional resolution. We find that with a centre-of-mass energy $E_{cm}=14 ~{TeV}$ at an integrated luminosity of 100 $fb^{-1}$ one may see evidence of hundreds of tri-photon events and a few four-photons events at the LHC, in addition to several thousands di-photon events. We also predict the event rates even at the early phase of LHC run.
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