Abstract
We investigate the impact of the direct searches for SUSY at LHC Run I on the naturalness of the Next-to-Minimal Supersymmetric Standard Model (NMSSM). For this end, we first scan the vast parameter space of the NMSSM to get the region where the fine tuning measures $\Delta_Z$ and $\Delta_h$ at the electroweak scale are less than about 50, then we implement by simulations the constraints of the direct searches on the parameter points in the region. Our results indicate that although the direct search experiments are effective in excluding the points, the parameter intervals for the region and also the minimum reaches of $\Delta_Z$ and $\Delta_h$ are scarcely changed by the constraints, which implies that the fine tuning of the NMSSM does not get worse after LHC Run I. Moreover, based on the results we propose a natural NMSSM scenario where the lightest neutralino $\tilde{\chi}_1^0$ as the dark matter (DM) candidate is Higgsino-dominated. In this scenario, $\Delta_Z$ and $\Delta_h$ may be as low as 2 without conflicting with any experimental constraints, and intriguingly $\tilde{\chi}_1^0$ can easily reach the measured DM relic density due to its significant Singlino component. We exhibit the features of the scenario which distinguish it from the other natural SUSY scenario, including the properties of its neutralino-chargino sector and scalar top quark sector. We emphasize that the scenario can be tested either through searching for $3 l + E_T^{miss}$ signal at 14 TeV LHC or through future DM direct detection experiments.
Highlights
In above formulae, Q denotes the renormalization scale in getting the effective potential, and its optimized value is usually taken as Q = √mt1mt2 with t1 and t2 being the light and heavy top squarks respectively
We investigate the impact of the direct searches for SUSY at LHC Run I on the naturalness of the Next-to-Minimal Supersymmetric Standard Model (NMSSM)
Our results indicate that the direct search experiments are effective in excluding the points, the parameter intervals for the region and the minimum reaches of ∆Z and ∆h are scarcely changed by the constraints, which implies that the fine tuning of the NMSSM does not get worse after LHC Run I
Summary
The NMSSM extends the MSSM by adding one gauge singlet superfield S, and since it aims at solving the μ problem of the MSSM, a Z3 discrete symmetry under which the Higgs superfields Hu,d and Sare charged is adopted to avoid the appearance of dimensionful parameters in its superpotential. These expressions indicate that the field H2 corresponds to the SM Higgs doublet with G+ and G0 denoting the Goldston bosons eaten by W and Z bosons respectively, and the field H1 represents a new SU(2)L doublet scalar field which has no tree-level couplings to the W/Z bosons These expressions indicate that the Higgs sector of the NMSSM includes three CP-even mass eigenstates h1, h2 and h3 which are the mixtures of the fields S1, S2 and S3, two CP-odd mass eigenstates A1 and A2 which are composed by the fields P1 and P2, as well as one charged Higgs H+. We assume mh3 > mh2 > mh and mA2 > mA1, and call the state hi the SM-like Higgs boson if its dominant component comes from the field S2. As for χ03, the relation |N35| > |N33| > |N34| usually holds
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