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The flow profile of the ejector directly affects the distribution of velocity and thermodynamic parameters such as pressure, temperature, and density, which are closely related to the internal irreversible loss of the ejector. This paper provides the performance investigation of an improved ejector with an optimal flow profile based on the Witozinsky curve for the first time. Faster contraction at the front part of the optimal profile helps to increase the fluid velocity, and slower contraction at the rear part could reduce the fluid fluctuation and boundary layer separation, which matches the fluid expansion better. It thus contributes to the reduction of irreversible internal losses and increases the efficiency of the ejector. Experiments were conducted under the same conditions to compare the performance superiority of the conventional and improved ejector. Results show that the entrainment ratio of the improved ejector could increase by as high as 19.2%. By testing the wall pressure distribution, the improvement of the entrainment ratio is attributed to the smaller velocity difference between the primary and secondary fluids at the nozzle exit. These results confirmed the potential application of the Witozinsky curve in ejector improvement and provided theoretical guidance for novel profile design.

Rare Higgs decays into a pair of heavy vector quarkonia, h→VV (V=J/Ψ, ϒ etc.), have been investigated in the standard model. Different from the past literature in which these decays are thought to be only dominated by the longitudinally polarized final states, we also include the transitions, which proceed through h→γ⁎γ⁎/h→Vγ⁎, followed by γ⁎→V. The final vector quarkonia via these ways are dominantly transversely polarized. Our calculation however shows that these transitions could lead to significant contributions to the decay rate, especially for the charmonium final states. The total branching ratios of these processes are predicted to be around 10−10, far below the current experimental upper bounds. Hopefully, experimental studies of these very rare decays in future high-precision experimental facilities might be interesting both to test the standard model and to look for new physics scenarios.

Exclusive rare Higgs decays into lepton pair plus one light hadron, such as h→ρ0(ω)ℓℓ¯, h→π0ℓℓ¯, h→π+(K+)ℓ−ν¯ℓ, and h→ρ+(K⁎+)ℓ−ν¯ℓ, have been explored in the standard model. Decay amplitudes are dominantly from the Higgs couplings to gauge bosons and to charged leptons, and their branching ratios are predicted in the range of 10−8∼10−5. We have also analyzed the differential dilepton invariant mass and angular distributions of h→ρ0ℓ+ℓ− decays. It will be challenging to search for these rare processes. Nevertheless, experimental studies of them, in particular, h→ρ0ℓ+ℓ− with ℓ=e,μ, might be interesting both to help deepen our understanding of the standard model and to probe new physics beyond the standard model in the future high-precision experiments.