QCD corrections to e+e- → H±W∓ in Type-I THDM at electron positron colliders

We investigate in detail the charged Higgs production associated with a W boson at electron-positron colliders within the framework of the Type-I two-Higgs-doublet model (THDM). We calculate the integrated cross section at the LO and analyze the dependence of the cross section on the THDM parameters and the colliding energy in a benchmark scenario of the input parameters of the Higgs sector. The numerical results show that the integrated cross section is sensitive to the charged Higgs mass, especially in the vicinity of m(H +/-) = similar or equal to 184 GeV at a 500 GeV e(+)e(-) collider, and decreases consistently with the increase of tan beta in the low tan beta region. The peak in the colliding energy distribution of the cross section arises from the resonance of the loop integrals, and it moves towards the low colliding energy with the increase of m(H +/-). We also study the two-loop NLO QCD corrections to both the integrated cross section and the angular distribution of the charged Higgs boson and find that the QCD relative correction is also sensitive to the charged Higgs mass and strongly depends on the final-state phase space. For tan beta = 2, the QCD relative correction at a 500 GeV e(+)e(-) collider varies in the range of [-10%, 11%] as increases from 150 to 400 GeV.