arXiv 1602.046922016-02hep-phhep-ex

750 GeV及以上的光子、光子喷流和暗光子

Photons, Photon Jets and Dark Photons at 750 GeV and Beyond

Basudeb Dasgupta, Joachim Kopp, Pedro Schwaller

备注：: 13 pages, 5 figures. V2: Improved detector simulation, journal version
发表信息：: Eur. Phys. J. C (2016) 76: 277
DOI：: 10.1140/epjc/s10052-016-4127-4

摘要：

在LHC涉及光子的新物理研究中，一个挑战是区分孤立光子的场景和导致“光子喷流”的模型。例如，在750 GeV双光子过剩的背景下，有人指出，真正的双光子共振$S \to γγ$可以通过形式为$p p \to S \to a a \to 4γ$的过程来模拟，其中$S$是质量为750 GeV的新标量，而$a$是衰变为两个共线光子的轻伪标量。通过利用大部分光子在内检测器内转换为$e^+e^-$对的事实，可以将光子射流与孤立光子区分开。在本说明中，我们量化这种歧视的权力，我们研究如何不同的光子射流相比，孤立的光子未来搜索的灵敏度。我们还研究了我们的结果如何依赖于粒子的寿命（S）衰减到光子射流。最后，我们讨论了对$S\to A^\prime A^\prime\to e^+e^-e^+e^-$的扩展，其中根本没有光子，但暗光子$A^\prime$衰变为$e^+e^-$对。我们的研究结果将是有用的，在未来的研究假定的750 GeV的信号，但也更普遍地在任何新的物理搜索涉及硬光子。

英文摘要：

In new physics searches involving photons at the LHC, one challenge is to distinguish scenarios with isolated photons from models leading to "photon jets". For instance, in the context of the 750 GeV diphoton excess, it was pointed out that a true diphoton resonance $S \to γγ$ can be mimicked by a process of the form $p p \to S \to a a \to 4γ$, where $S$ is a new scalar with a mass of 750 GeV and $a$ is a light pseudoscalar decaying to two collinear photons. Photon jets can be distinguished from isolated photons by exploiting the fact that a large fraction of photons convert to an $e^+e^-$ pair inside the inner detector. In this note, we quantify this discrimination power, and we study how the sensitivity of future searches differs for photon jets compared to isolated photons. We also investigate how our results depend on the lifetime of the particle(s) decaying to the photon jet. Finally, we discuss the extension to $S\to A^\prime A^\prime\to e^+e^-e^+e^-$, where there are no photons at all but the dark photon $A^\prime$ decays to $e^+e^-$ pairs. Our results will be useful in future studies of the putative 750 GeV signal, but also more generally in any new physics search involving hard photons.

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