Search for K⁺ decays into the π⁺e⁺e^-e⁺e^- final state

2023/07/10 by NA62 Collaboration
#FOS: Physical sciences #High Energy Physics - Experiment (hep-ex)

paper · doi:10.48550/arxiv.2307.04579

Abstract

The first search for ultra-rare K⁺ decays into the π⁺e⁺e^-e⁺e^- final state is reported, using a dataset collected by the NA62 experiment at CERN in 2017-2018. An upper limit of 1.4× 10^-8 at 90% CL is obtained for the branching ratio of the K⁺→π⁺e⁺e^-e⁺e^- decay, predicted in the Standard Model to be (7.2±0.7)× 10^-11. Upper limits at 90% CL are obtained at the level of 10^-9 for the branching ratios of two prompt decay chains involving pair-production of hidden-sector mediators: K⁺→π⁺aa, a→ e⁺e^- and K⁺→π⁺S, S→ A^′ A^′, A^′→ e⁺e^-.

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