No abstract

Inspired by the recent CMS h → µτ excess, we calculate the lepton flavor violating Higgs decay h → µτ in the littlest Higgs model with T-parity (LHT). Under the constraints of ℓ i → ℓ j γ, Z → ℓ ilj and Higgs data, we find that the branching ratio of h → µτ can maximally reach O(10 −4 ). We also investigate the correlation between h → µτ , τ → µγ and Z → µτ , which can be used to test LHT model at future e + e − colliders.

We investigate indirect constraints on the top partner within the minimal fermionic top partner model. By performing a global fit of the latest Higgs data, B s → μ + μ − measurements and the electroweak precision observables we find that the top partner with the mass up to 830 GeV is excluded at 2σ level. Our bound on the top partner mass is much stronger than the bounds obtained from the direct searches at the LHC. Under the current constraints the fine-tuning measure is less than 9% and the branching ratio of T → tZ is bounded between 14% and 25%. We also find that precise measurements of Higgs couplings at 240 GeV TLEP will constrain the top partner mass in multi-TeV region.

The measurement of Higgs self-coupling is one of the most crucial physics goals at the future colliders. At the LHC, the di-Higgs production is a main way to measure the Higgs trilinear coupling. As a complementary to the di-Higgs production, tthh process may open a new avenue to measure di-Higgs physics at the LHC and a future 100 TeV pp collider or a high energy e + e − collider since the extra tt in the final states may efficiently suppress the backgrounds. However, such a kind of process is also controlled by the topHiggs coupling. In this work, we investigate the impact of CP-violating top-Higgs coupling on tthh production at the LHC, e + e − and a 100 TeV hadron collider under the current Higgs data. Within 2σ Higgs data allowed parameter region, we find that the cross section of tthh at the LHC-14 TeV, e + e − -1 TeV and VHE-LHC/SPPC-100 TeV can be enhanced up to 2.1 times the SM predictions. The future precise measurement of Higgs coupling will reveal the nature of top-Higgs interaction and improve the sensitivity of the determination of Higgs self-coupling through tthh production.