Search

The determination of the Higgs self coupling is one of the key ingredients for understanding the mechanism behind the electroweak symmetry breaking. An indirect method for constraining the Higgs trilinear self coupling via single Higgs production at next-to-leading order (NLO) has been proposed in order to avoid the drawbacks of studies with double Higgs production. In this paper we study the Higgs self interaction through the vector boson fusion (VBF) process $e^{-} p \to \nu_{e} h j$ at the future LHeC. At NLO level, we compute analytically the scattering amplitudes for relevant processes, in particular those induced by the Higgs self interaction. A Monte Carlo simulation and a statistical analysis utilizing the analytic results are then carried out for Higgs production through VBF and decay to $b\bar{b}$, which yield for the trilinear Higgs self-coupling rescaling parameter $\kappa_{\lambda}$ the limit [-0.57, 2.98] with $2~\text{ab}^{-1}$ integrated luminosity. If we assume about 10% of the signal survives the event selection cuts, and include all the background, the constraint will be broadened to [-2.11, 4.63]., Comment: 19 pages, 7 figures, 2 tables

Large Hadron Collider (LHC) has provided direct evidence of Yukawa couplings between the third generation charged fermions and the 125 GeV Higgs boson. Whether the first two generation charged fermions arise from exactly the same mechanism becomes the next interesting question. Therefore, direct measurements of charm or muon Yukawa couplings will be crucial to answering this puzzle. The charm Yukawa measurement at the LHC suffers from severe QCD background and it is extremely difficult to reach the sensitivity. In this paper, we compare the potential of probing charm Yukawa coupling at the two proposed future "Higgs Factory" experiments, the Large Hadron electron Collider (LHeC) and Circular electron positron collider (CEPC). At the LHeC, Higgs bosons will be produced via weak boson fusion and the energetic forward jet may suppress the background significantly. However, due to huge $\gamma-g$ scattering background, the potential of LHeC search is still limited. With $-80\%$ polarized electron beam of 60 GeV, the signal significance can only reach $2\sigma$ for $ \kappa_{c}\simeq 1$ with a 3 ab$^{-1}$ integrated luminosity. In comparison, measurement at the CEPC can then reach $8.0\sigma$ for $\kappa_{c}\simeq 1$ with a 2 ab$^{-1}$ of data.

The search for the light Higgsino in the minimal supersymmetric standard model is a crucial test of the naturalness criteria in supersymmetry. On the other hand, the direct production of light Higgsinos is also known as one of the most challenging supersymmetry searches at the LHC. The lack of visible leptons due to the compressed spectrum and their small production rates limit their discovery potential in both monojet plus ET events and weak boson fusion (WBF) production. The signal-to-background ratio prediction is usually within the background systematic uncertainties at the LHC. Without color exchange between the beams, e−p colliders are well known to exhibit WBF. Therefore, we search for light Higgsinos at two future e−p colliders at CERN: the Large Hadron electron Collider (LHeC) and the Future Circular Collider in hadron-electron mode (FCC-eh). The light Higgsinos will be produced in pairs through weak boson fusion with controlled background at these colliders. We find that a 95/145 GeV Higgsino can be reached at the 2σ level at the future LHeC/FCC-eh with a luminosity of 3 ab−1, respectively.

The precision measurement of the WWγ vertex at the future Large Hadron electron Collider (LHeC) at CERN is discussed in this paper. We propose to measure this vertex in the e−p→e−W±j channel as a complement to the conventional charged current νeγj channel. In addition to the cross section measurement, χ2 method studies of angular variables provide powerful tools to probe the anomalous structure of triple gauge boson couplings. We study the distribution of the well-known azimuthal angle between the final state forward electron and jet in this vector-boson fusion process. On the other hand, full reconstruction of leptonic W decay opens a new opportunity to measure W polarization that is also sensitive to the anomalous triple gauge boson couplings. Taking into consideration the superior determination of parton distribution functions based on future LHeC data, the constraints of λγ and Δκγ might reach up to O(10−3) level in the most ideal case with the 2–3 ab−1 data set, which shows a potential advantage compared to those from LHC and Large Electron-Positron Collider (LEP) data.