Light Higgsino Decays as a Probe of the NMSSM

TL;DR

This paper explores how light Higgsino decays in the NMSSM can be used to detect and differentiate it from the MSSM at the LHC, especially in low mass gap scenarios with small missing energy.

Contribution

It demonstrates the viability of the 4b+j+E_Tmiss signal as a search channel for light Higgsinos in the NMSSM at the 14 TeV LHC and discusses how combined collider and detection data can distinguish NMSSM from MSSM.

Findings

The 4b+j+E_Tmiss signal can effectively probe low mass gap regions at the LHC.

Collider signals combined with direct detection can differentiate NMSSM from MSSM.

Light Higgsinos decay into singlinos and Higgs, producing distinctive collider signatures.

Abstract

In the Next-to Minimal Supersymmetric Standard Model (NMSSM), a sizable coupling $\lambda$ between the singlet and Higgs fields can naturally accommodate the observed Higgs boson mass of 125 GeV. This large coupling also results in a large separation between the Higgsino and singlino mass scales in the neutralino sector to evade stringent constraints from direct detection experiments. Most of the natural parameter space in this setup therefore contains light Higgsinos that can decay into the singlino and the 125 GeV Higgs. If the Higgsinos are to be light enough to be produced at the LHC, the mass gap $m_{\tilde\chi^0_2} -(m_{\tilde\chi^0_1} +m_h)$ is generally fairly low, resulting in small missing energy. We study the collider phenomenology of this process and demonstrate that the 4$b+j+{E\!\!\!\!/_{\rm T}}$ signal arising from $pp\rightarrow\tilde\chi_i^0\tilde\chi_j^0jj$ process can be a viable channel to search for this low mass gap region at the 14 TeV LHC. In addition, we find that a potential signal from the LHC search, in tandem with direct detection experiments, can distinguish the NMSSM from the analogous process in the MSSM, where the bino plays the role of the singlino, for positive values of the $\mu$ parameter even when the additional singlet-dominated (pseudo)scalars are absent or indistinguishable from the Higgs in the decay.