ATLAS on-Z excess via gluino-Higgsino-singlino decay chains in the NMSSM

Recently the ATLAS experiment has reported 3.0 σ excess in an on- Z signal region in searches for supersymmetric particles. We find that the next-to-minimal supersymmetric standard model can explain this excess by the production of gluinos which mainly decay via g ˜ → g χ ˜ 2 , 3 0 → g Z χ ˜ 1 0 g~→gχ~02,3→gZχ~01 where χ ˜ 2 , 3 0 χ~02,3 and χ ˜ 1 0 χ~01 are the Higgsino and the singlino-like neutralinos, respectively. We show that the observed dark matter density is explained by the thermal relic density of the singlino-like neutralino, simultaneously. We also discuss the searches for the Higgs sector of this scenario at the Large Hadron Collider.