Explanation of the ATLAS Z-peaked excess by squark pair production in the NMSSM

TL;DR

This paper proposes that squark pair production within the NMSSM can explain the ATLAS Z-peaked excess, offering a viable alternative to gluino-based interpretations and predicting testability at the 14 TeV LHC.

Contribution

It introduces a novel squark-based explanation for the ATLAS Z excess in the NMSSM, expanding the viable parameter space compared to gluino-based models.

Findings

Squark masses up to 1.2 TeV can explain the excess.

More than 10 signal events are possible for squark masses below 750 GeV.

The squark explanation is testable at the 14 TeV LHC.

Abstract

The ATLAS collaboration recently reported a $3\sigma$ excess in the leptonic-$Z+jets+E_{T}^{miss}$ channel. We intend to interpret this excess by squark pair production in the Next-to-Minimal Supersymmetric Standard Model (NMSSM). The decay chain we employ is $\tilde{q} \to q \tilde{\chi}_2^0 \to q \tilde{\chi}_1^0 Z$, where $\tilde{\chi}_1^0$ and $\tilde{\chi}_2^0$ denote the lightest and the next-to-lightest neutralinos with singlino and bino as their dominant components respectively. Our simulations indicate that after considering the constraints from the ATLAS searches for $jets + E_{T}^{miss}$ signal the central value of the excess can be obtained for $m_{\tilde{q}} \lesssim 1.2 {\rm TeV}$, and if the constraint from the CMS on-$Z$ search is further considered, more than 10 signal events are still attainable for $m_{\tilde{q}} \lesssim 750 {\rm GeV}$. Compared with the interpretation by gluino pair production, the squark explanation allows for a significantly wider range of $m_{\tilde{q}}$ as well as a less compressed SUSY mass spectrum. We also show that the squark explanation will be readily tested at the initial stage of the 14 TeV LHC.