Explanation of the ATLAS Z-peaked excess in the NMSSM

A bstractRecently the ATLAS collaboration reported a 3σ excess in the leptonic-Z + jets + ETmiss channel. This may be interpreted in the Next-to-Minimal Supersymmetric Standard Model (NMSSM) by gluino pair production with the decay chain g˜→qq¯χ˜20→qq¯Zχ˜10$$ \tilde{g}\to q\overline{q}{\tilde{\chi}}_2^0\to q\overline{q}Z{\tilde{\chi}}_1^0 $$, where χ˜10$$ {\tilde{\chi}}_1^0 $$ and χ˜20$$ {\tilde{\chi}}_2^0 $$ denote the lightest and the next-to-lightest neutralinos with singlino and bino as their dominant components respectively. After exploring the relevant parameter space of the NMSSM by considering the constraints from the ATLAS searches for jets + ETmiss signals, we conclude that the NMSSM is able to explain the excess at 1σ level with the number of the signal events reaching its measured central value in optimal cases, and the best explanation comes from a compressed spectrum such as mg˜≃650$$ {m}_{\tilde{g}}\simeq 650 $$ GeV, mχ˜20≃565$$ {m}_{{\tilde{\chi}}_2^0}\simeq 565 $$ and mχ˜10≃465$$ {m}_{{\tilde{\chi}}_1^0}\simeq 465 $$ GeV. We also check the consistency of the ATLAS results with the null result of the CMS on-Z search. We find that under the CMS limits at 95% C.L., the event number of the ATLAS on-Z signal can still reach 11 in our scenario, which is about 1.2σ away from the measured central value.