Abstract
In this paper, motivated by the observation that the Standard Model predictions are now above the experimental data for the mass difference ΔMs(d), we perform a detailed study of Bs(d) − overline{B} s(d) mixing and Bs → μ+μ− decay in the ℤ3-invariant NMSSM with non-minimal flavour violation, using the recently developed procedure based on the Flavour Expansion Theorem, with which one can perform a purely algebraic mass-insertion expansion of an amplitude written in the mass eigenstate basis without performing any diagrammatic calculations in the interaction/flavour basis. Specifically, we consider the finite orders of mass insertions for neutralinos but the general orders for squarks and charginos, under two sets of assumptions for the squark flavour structures (i.e., while the flavour-conserving off-diagonal element δ33LR is kept in both of these two sectors, only the flavour-violating off-diagonal elements δ23LL and δi3RR (i = 1, 2) are kept in the LL and RR sectors, respectively). Our analytic results are then expressed directly in terms of the initial Lagrangian parameters in the interaction/flavour basis, making it easy to impose the experimental bounds on them. It is found numerically that the NMSSM effects with the above two assumptions for the squark flavour structures can accommodate the observed deviation for ΔMs(d), while complying with the experimental constraints from the branching ratios of Bs → μ+μ− and B → Xsγ decays.
Highlights
SM-like Higgs boson [7, 8], which has imposed strong constrains on the parameter space of MSSM [9,10,11]
In this paper, motivated by the observation that the Standard Model predictions are above the experimental data for the mass difference ∆Ms(d), we perform a detailed study of Bs(d) − Bs(d) mixing and Bs → μ+μ− decay in the Z3-invariant Next-to-Minimal Supersymmetric Standard Model (NMSSM) with non-minimal flavour violation, using the recently developed procedure based on the Flavour Expansion Theorem, with which one can perform a purely algebraic mass-insertion expansion of an amplitude written in the mass eigenstate basis without performing any diagrammatic calculations in the interaction/flavour basis
Among the various non-minimal SUSY models, the Next-to-Minimal Supersymmetric Standard Model (NMSSM) [12,13,14,15], the simplest extension of the MSSM with a gauge singlet superfield, has the capability to fix these shortcomings of the MSSM, and alleviates the tension implied by the lack of any evidence for superpartners below the EW scale [16]
Summary
At the Lagrangian level, the Z3-invariant NMSSM differs from the MSSM by the superpotential and the soft SUSY breaking part. Where WMSSM μ=0 is the MSSM superpotential but without the μ term [78, 79], and Sdenotes the Higgs singlet superfield, while Hu = (Hu+, Hu0)T and Hd = (Hd0, Hd−)T are. The dimensionless parameters λ and κ can be complex in general, but are real in the CPconserving case. With the scalar components of the Higgs doublet and singlet superfields being denoted by Hu, Hd, and S, respectively, the soft SUSY breaking Lagrangian of the Z3-invariant NMSSM is given by [76, 77]. While the mass parameter m2S is real, the trilinear couplings Aλ and Aκ are generally complex, but are real in the CP-conserving case, as is assumed throughout this paper
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