Search for singly charged Higgs bosons in vector-boson scattering at ep colliders

We search for the fiveplet singly charged Higgs H-5(+/-) in the Georgi- Machacek model at the ep colliders. The charged Higgs bosons are produced via the ZW(+/-) fusion process pe(-) -> je(-) H-5(+/-) and decay as H-5(+/-) -> ZW(+/-) -> (l(+)l(-))(jj). With a detector-level simulation at the FCC-eh and LHeC, a multivariate analysis is performed to yield limits on the production cross section times branching ratio sigma(pe(-) -> je(-)H(5)(+/-)) x BR(H-5(+/-) -> ZW(+/-)) and on the model parameter sin theta(H) for charged Higgs masses between 200 and 1000 GeV. Considering 10% systematic uncertainty on the background, at the FCC-eh (LHeC) with 1 ab(-1) integrated luminosity, for a mass of H-5(+/-) 600 (200) GeV, the cross section corresponding to the 2-sigma significance is 0.59 (3.69) fb, corresponding to a 2-sigma limit on the sin theta(H) is 0.15 (0.41). The effects of -80% and +80% electron beam polarizations are also investigated and found to be small for this study.