Jeonghyeon Song

Role of h → ηη in intermediate-mass higgs boson searches at the large hadron collider

The dominance of the h-->etaeta decay mode for the intermediate-mass Higgs boson is highly motivated to solve the little hierarchy problem and to ease the tension with the precision data. However, the discovery modes for m(h) approximately <150 GeV, h-->gammagamma, and W/Zh-->(lnu/ll)(bb), will be substantially affected. In this Letter, we show that h-->etaeta-->4b is complementary and we can use this decay mode to detect the intermediate Higgs boson at the LHC, via Wh and Zh production. Requiring at least one charged lepton and 4B tags in the final state, we can identify a clean Higgs boson signal for m(h) approximately <150 GeV with a high significance and with a full Higgs mass reconstruction. We use the next-to-minimal supersymmetric standard model and the simplest little Higgs model for illustration.

Comprehensive study of two Higgs doublet models in light of the new boson with mass around 125 GeV

A bstractA new boson of mass roughly 125 GeV has been recently reported by the ATLAS and CMS collaborations. Although its signals in various decay modes resemble those of the standard model (SM) Higgs boson, observed are the combinations of entangled information about the production, decay rates and total decay width of the new boson. In addition, some decay channels show non-negligible deviation from the SM expectation, such as the 2σ excess in the diphoton channel. In the four types (I, II, X and Y) of two Higgs doublet models, we perform the global χ2 fit in three scenarios: (i) the new boson is the light CP-even Higgs boson h0; (ii) it is the heavy CP-even Higgs boson H0; (iii) the signals are from the degenerate state of h0 and the pseudoscalar A0. Considering other phenomenological constraints such as flavor physics, electroweak precision data, and the LEP search for the Higgs boson, we find that the first scenarios in Type II provides the best fit. And the other models are also as good as the SM in explaining the LHC Higgs data.

Kinematic Cusps: Determining the Missing Particle Mass at Colliders

Abstract In many extensions of the SM, neutral massive stable particles (dark matter candidates) are produced at colliders in pairs due to an exact symmetry called a “parity”. These particles escape detection, rendering their mass measurement difficult. In the pair production of such particles via a specific (“antler”) decay topology, kinematic cusp structures are present in the invariant mass and angular distributions of the observable particles. Together with the end-points, such cusps can be used to measure the missing particle mass and the intermediate particle mass in the decay chain. Our simulation of a benchmark scenario in a Z ′ supersymmetric model shows that the cusp feature survives under the consideration of detector simulation and the standard model backgrounds. This technique for determining missing particle masses should be invaluable in the search for new physics at the LHC and future lepton colliders.

Two Higgs doublet models for the LHC Higgs boson data at \( \sqrt{s} \) = 7 and 8 TeV

A bstractUpdated LHC data on the new 126 GeV boson during the 7 and 8 TeV runnings strengthen the standard model Higgs boson interpretation further. Through global χ2 fit analysis, we investigate whether the new particle could be one of the scalar particles in two Higgs doublet models. Four types of the model (I, II, X and Y) are comprehensively studied. Considering the recent analysis on the spin-parity of the new boson, we take two scenarios: it is either the lighter CP-even one or the heavier CP-even one. It is found that the current LHC Higgs data constrain the model quite strongly. Only narrow region along the decoupling line and a separate small island are allowed in Type II, X, and Y. Type I is exceptional with much larger allowed space. We also find that the current data are compatible with the possibility that the light Higgs boson h0 is hidden in the mass window of 90-100 GeV.

Analysis of CP violation in neutralino decays to tau sleptons

In the minimal supersymmetric (SUSY) standard model, tau sleptons

Constraint of B0d,s - B̄0d,s mixing on warped extra-dimension model

{\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{\ensuremath{\tau}}}_{1,2}

How resonance-continuum interference changes 750 GeV diphoton excess: signal enhancement and peak shift

and neutralinos

Neutralino production and decay at an e+e− linear collider with transversely polarized beams

{\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{\ensuremath{\chi}}}_{1,2}^{0}

A minimal supersymmetric scenario with only μ at the weak scale

are expected to be among the lightest supersymmetric particles that can be produced copiously at future

Muon anomalous magnetic moment and the heavy photon in a little Higgs model

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