Photons, photon jets, and dark photons at 750 GeV and beyond

Dasgupta, Basudeb; Kopp, Joachim; Schwaller, Pedro

doi:10.1140/epjc/s10052-016-4127-4

Journal Article

PUBDB-2016-02425

Photons, photon jets, and dark photons at 750 GeV and beyond

Dasgupta, B. (Corresponding author) ; Kopp, J. (Corresponding author) ; Schwaller, P. (Corresponding author)DESY*

2016
Springer Berlin

The European physical journal / C 76(5), 277 (2016) [10.1140/epjc/s10052-016-4127-4]

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Please use a persistent id in citations: doi:10.1140/epjc/s10052-016-4127-4

Report No.: DESY-16-028; MITP-16-020; TIFR-TH-16-05; arXiv:1602.04692

Abstract: 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 $S \to \gamma\gamma$ can be mimicked by a process of the form $pp \to S \to aa \to 4\gamma$, where $S$ is a new scalar with a mass of 750 GeV and $a$ is alight 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 thelifetime 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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