Quantum effects on Higgs-strahlung events at linear colliders within the general two-Higgs-doublet model

The associated production of neutral Higgs bosons with the Z{sup 0} gauge boson (h{sup 0}Z{sup 0}, H{sup 0}Z{sup 0}) is investigated in the context of the future linear colliders, such as the ILC and CLIC, within the general two-Higgs-doublet model (2HDM). We compute the corresponding cross section for the processes e{sup +}e{sup -{yields}}Z{sup 0}h{sup 0}/Z{sup 0}H{sup 0} at one-loop, including the full set of corrections at O({alpha}{sub ew}{sup 3}) together with the leading O({alpha}{sub ew}{sup 4}) terms, in full consistency with the available theoretical and phenomenological constraints. We find that the wave-function corrections to the external Higgs fields are the dominant source of the quantum effects, which turn out to be large and negative (e.g., {delta}{sigma}/{sigma}{approx}-20%/-60%) in all the {radical}(s) range, and located predominantly in the region around tan{beta}{approx}1 and moderate values of the parameter {lambda}{sub 5} (being {lambda}{sub 5}<0). This behavior can be ultimately traced back to the enhancement potential of the triple Higgs-boson self-couplings, a trademark feature of the 2HDM with no counterpart in the Higgs sector of the minimal supersymmetric standard model. Even under this substantial depletion of the one-loop-corrected signal (which is also highly distinctive with respect to the SM expectation for e{sup +}e{sup -{yields}}Z{sup 0}H),more » the predicted Higgs-strahlung rates comfortably reach a few tens of femtobarn, which means barely {approx}10{sup 3}-10{sup 4} events per 500 fb{sup -1} of integrated luminosity. Because of their great complementarity, we argue that the combined analysis of the Higgs-strahlung events (h{sup 0}Z{sup 0}, H{sup 0}Z{sup 0}) and the previously computed one-loop Higgs-pair production processes (H{sup 0}A{sup 0}) could be instrumental to probe the structure of the Higgs sector at future linac facilities.« less