Z-boson decays into an invisible massless dark photon at FCC-ee
Abstract
We study the decay of the Z vector boson into a photon and a massless (invisible) dark photon at FCC ee. The photon can be used as a trigger for the event, while the dark photon is detected indirectly as missing momentum in the event final state. The main irreducible bakground comes from the process e+e− → Z γ → νν ̄γ, whose impact can be reduced by cutting on the detected photon energy. This process can be affected by additional background contamination in the presence of crack regions of the detector: their existence can indeed increase the impact of the otherwise 1/s suppressed background from e+e− → l+ l- γ , where either leptons are not detected. The best result found for the lepton collider running at the Z mass shows a final sensitivity to branching ratios of order O(10-11) in the absence of crack regions. We also discuss how to use the photon angular distribution of the events in lepton collisions to discriminate between the dark photon and a pseudoscalar state like the axion.
Bibliography
- Z-boson decays into an invisible dark photon at the LHC, HL-LHC and future lepton colliders M. Cobal, C. De Dominicis, M. Fabbrichesi, E. Gabrielli, J. Magro, B. Mele, and G. Panizzo Phys. Rev. D 102, 035027
People
Interest from:
- G. Panizzo et al, Università di Udine