Explanation of the ATLAS Z-peaked excess in the NMSSM

摘要: Recently the ATLAS collaboration reported a 3 sigma excess in the leptonic-Z + jets + E-T(miss) channel. This may be interpreted in the Next-to-Minimal Supersymmetric Standard Model (NMSSM) by gluino pair production with the decay chain (g) over tilde -> q (q) over bar(chi) over tilde (0)(2) -> q (q) over barZ (chi) over tilde (0)(1), where (chi) over tilde (0)(1) and (chi) over tilde (0)(2) 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 + E-T(miss) signals, we conclude that the NMSSM is able to explain the excess at 1 sigma 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 m((g) over tilde) similar or equal to 650 GeV, m((chi) over tilde2)(0) similar or equal to 565 GeV and m((chi) over tilde1)(0) similar or equal to 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 1.2 sigma away from the measured central value.