[Paper Review] Implications of Higgs Sterility for the Higgs and Stop Sectors

J. Guo, Zhaofeng Kang+2 more|arXiv (Cornell University)|Aug 14, 2013

Particle physics theoretical and experimental studies3 citations

TL;DR

This paper investigates the implications of a highly SM-like (sterile) Higgs boson on the Higgs and stop sectors in the MSSM and NMSSM. It shows that in the MSSM, Higgs sterility imposes a lower bound of $ M_A \gtrsim 900 $ GeV due to doublet-doublet mixing, while stop masses remain unconstrained due to the heavy Higgs mass. In contrast, in the NMSSM, Higgs sterility significantly constrains the stop sector due to light stops, enabling new LHC signatures such as same-sign leptons and multi-jets via stop-sbottom decays.

ABSTRACT

The LHC data implies that the newly discovered Higgs boson h may be sterile (highly SM-like). In supersymmetric SMs (SSMs), Higgs couplings are often modified by Higgs mixing and stop loop corrections, so we study the Higgs sterility in the Higgs and stop sectors in two SSMs: (I) The Minimal SSM (MSSM). In the nearly decoupling region, the doublet-doublet mixing effect can only enhance C_{hb\bar b} by 2m_Z^2/M_A^2. Sterility places M_A\gtrsim 900 GeV. But it hardly constrains the stop sector due to the heaviness of Higgs boson mass m_h; (II) The next to MSSM(NMSSM). In the presence of doublet-singlet mixing, the mixing structure is complicated. We find a simple approximation to understand Higgs sterility and its implications, says the amount of pushing-up m_h\lesssim 5 GeV while the pulling-down scenario is favored. Stops can be light here, so Higgs sterility significantly constrains them directly and indirectly except for blind spots. We also study the LHC features of the whole stop sector facing a sterile Higgs and find that, in virtue of decays between stops and sbottom, characteristic signatures like same-sign leptons and multi b-jets are promising probes.

Motivation & Objective

• To analyze how a highly SM-like (sterile) Higgs boson at 126 GeV constrains the Higgs and stop sectors in supersymmetric models.
• To examine the role of doublet-doublet and doublet-singlet mixing in modifying Higgs couplings and mass predictions.
• To assess the impact of Higgs sterility on stop sector phenomenology, particularly in the context of LHC discovery potential.
• To identify characteristic LHC signatures arising from stop and sbottom decays under sterile Higgs conditions.

Proposed method

• Analytical study of Higgs mixing effects in the MSSM, focusing on the $ 1/M_A^2 $ suppression of doublet-doublet mixing.
• Use of a simplified approximation to model doublet-singlet mixing in the NMSSM and its impact on $ m_h $ and Higgs couplings.
• Derivation of Higgs signal strength ratios $ R_{gg}^{H_i}(X) $ using reduced couplings $ r_{i,X} $, relating to experimental observables.
• Construction of stop mass square matrices in the $ (\widetilde{t}_R, \widetilde{t}_L) $ basis and calculation of mass eigenstates via diagonalization.
• Evaluation of stop mixing angles $ \theta_{\widetilde{t}} $ and their dependence on $ A_t $, $ \mu $, and $ \tan\beta $.
• Preliminary analysis of LHC signatures from stop-sbottom cascades, emphasizing same-sign leptons and multi-b-jet final states.

Experimental results

Research questions

• RQ1 How does Higgs sterility constrain the pseudoscalar mass $ M_A $ in the MSSM?
• RQ2 What are the implications of doublet-singlet mixing for Higgs mass and couplings in the NMSSM under Higgs sterility?
• RQ3 How light can the stop sector be in the NMSSM while remaining consistent with a sterile Higgs boson?
• RQ4 What are the dominant decay chains involving stops and sbottoms in the presence of a sterile Higgs?
• RQ5 Which LHC signatures are most promising for probing the stop sector under sterile Higgs conditions?

Key findings

• In the MSSM, Higgs sterility requires $ M_A \gtrsim 900 $ GeV due to doublet-doublet mixing, with the mixing effect suppressed as $ 2m_Z^2/M_A^2 $.
• The stop sector in the MSSM remains largely unconstrained by Higgs sterility due to the high Higgs mass, except in extreme limits.
• In the NMSSM, doublet-singlet mixing can either push up or pull down $ m_h $, with the shift bounded by Higgs sterility constraints.
• Light stops in the NMSSM are significantly constrained by Higgs sterility, both directly and indirectly, except at blind spots.
• Stop-sbottom decays in the NMSSM lead to characteristic LHC signatures, including same-sign leptons and multi-b-jet final states.
• These signatures offer a promising probe for the stop sector in models with a sterile Higgs boson.