Diphotons at the $Z$-pole in Models of the 750 GeV Resonance Decaying to Axion-Like Particles

Abstract

Models in which the 750 GeV resonance ($S$) decays to two light axion-like particles (ALPs $a$), which in turn decay to collimated photons mimicking the observed signal, are motivated by Hidden Valley scenarios and could also provide a mechanism by which a $S\to \gamma \gamma$ signal persists while $S\to Z\gamma ,ZZ$ and $WW$ remain subdued in the near future. We point out that these Hidden Valley like models invoking $S\to aa\to 4\gamma$ must also contend with $Z\to a(\to \gamma \gamma )\gamma$ constraints coming from CDF and ATLAS. Within an effective field theory framework, we work out the constraints on the couplings of $S$ to $a$ and gauge bosons coming from photonic $Z$ decays and ensuring that the ALPs decay inside the electromagnetic calorimeter, in two regimes - where $a$ decays primarily to photons, and where $a$ also has hadronic branchings. The analysis is done for both when $S$ has a large as well as a narrow width, and for different relative contributions to the signal coming from $S\to \gamma \gamma$ and $a\to \gamma \gamma$. Results for the particular case where $S$ and $a$ belong to the same complex field are also presented. A $\gamma \gamma$ resonance at the $Z$-pole coming from $Z\to a\gamma$ is expected in this class of models. Taking benchmark ALP masses below around 0.4 GeV and, assuming reasonable values for the fake jet rate and the identification efficiency of the photon-jet, we find the prospects for the discovery of diphotons at the $Z$-pole.

19 pages, 11 figures

References in corpus (16)

• PYTHIA 6.4 Physics and Manual
• The automated computation of tree-level and next-to-leading order differential cross sections, and their matching to parton shower simulations
• Echoes of a Hidden Valley at Hadron Colliders
• Revisiting the SN1987A gamma-ray limit on ultralight axion-like particles
• Discovering the Higgs Through Highly-Displaced Vertices
• Phenomenology of a 750 GeV Singlet
• The Need for Purely Laboratory-Based Axion-Like Particle Searches
• Tricking Landau-Yang: How to obtain the diphoton excess from a vector resonance
• The 750 GeV $S$-cion: Where else should we look for it?
• Experimental Considerations Motivated by the Diphoton Excess at the LHC
• Jets and Photons
• Photons, Photon Jets and Dark Photons at 750 GeV and Beyond
• The NMSSM lives: with the 750 GeV diphoton excess
• Diphotons from Diaxions
• Interpreting 750 GeV Diphoton Excess in Plain NMSSM
• Re-opening dark matter windows compatible with a diphoton excess

Cited by in corpus (8)

• Dark photon relic dark matter production through the dark axion portal
• Probing axion-like particles with $\gamma \gamma$ final states from vector boson fusion processes at the LHC
• Axions: From Magnetars and Neutron Star Mergers to Beam Dumps and BECs
• ALP-portal majorana dark matter
• Probing HNL-ALP couplings at colliders
• ALPs and HNLs at LHC and Muon Colliders: Uncovering New Couplings and Signals
• Visible GeV ALP from TeV Vector-like Leptons
• Same-Sign Taus Signatures of Maximally Flavor-Violating Scalars at the LHC