We report on studies of the $e^+e^- \to HZ$ process with the subsequent decay of the Higgs boson $H \to Z Z^\star$, where the $Z Z^\star$ combination is reconstructed in the final states with two jets and two leptons. The analysis is performed using Monte Carlo data samples obtained with detailed ILD detector simulation assuming the integrated luminosity 2 ab$^{-1}$, the beam polarizations...
Precision measurements of the properties of the discovered Higgs boson are one of the main programs at current and future collider experiments. At the international linear collider with the center-of-mass energy 250 GeV, e+e- → hZ is the dominant Higgs production process, and the cross section would be measured with a few percent accuracies. In this talk, we present the cross section of the...
In many analyses in Higgs, top and electroweak physics, the kinematic reconstruction of the final state is improved by constrained fits. This is a particularly powerful tool at $e^{+}e^{-}$ colliders, where the initial state four-momentum is known and can be employed to constrain the final state. A crucial ingredient to kinematic fitting is an accurate estimate of the measurement...
In the Standard Model（SM）, $h \gamma Z$ coupling is a loop induced coupling, therefore it might receive relatively large correction from Beyond Standard Model（BSM） physics. It is very challenging to measure at the HL-LHC, where only 3$\sigma$ significance is expected for branching ratio of $h \to \gamma Z$.
On the other hand, $h \gamma Z$ coupling is potentially very sensitive to new...
Recently, it has been discussed that a possibility of primordial black holes is generated from the first-order phase transition at high or low temperatures. We consider the primordial black hole production during first-order electroweak phase transition. In this talk, we discuss the comprehensive test of the model with strongly first-order electroweak phase transition at the measurement of hhh...
In this talk, we discuss whether a multi-step electroweak phase transition (EWPT) occurs in two Higgs doublet models (2HDMs). We examine parameter regions in CP-conserving 2HDMs and find certain areas where the multi-step EWPTs occur. In addition, we compute the Higgs trilinear coupling in the parameter region where the multi-step EWPTs occur, which has the tendency to be large in a certain...
