Analysis of trilinear Higgs self coupling in Two Higgs Doublet model at lepton collider

Abstract

The deduction of trilinear Higgs coupling is the main incentive behind building of future lepton colliders. The scalar sector of the Standard Model (SM) when modified by inserting another Higgs doublet and quadratic Higgs potential brings many new features into the model and as a result some extra trilinear Higgs self couplings also emerge. Reconstruction of Higgs potential relies on trilinear Higgs self-coupling which further depends upon the Higgs boson masses. In this study, computational analysis of neutral Higgs bosons h, H and A is carried out within the parameter space of Two Higgs Doublet Model (2HDM) type-I in exact alignment limit of sin (β − α) = 1 at compact linear collider. Assuming Compact Linear Collider (CLIC) scenario where the electron-positron beams will be collided at √ s = 1.5 TeV. Two different values of predicted integrated luminosities are used in our calculations, 1000 f b −1 and 2500 f b −1 . Three signal processes e + e − → Zhh → jjb bb b, e + e − → ZHH → jjb bb b and e + e − → Zhh → jjb bb b are selected for analysis. The polarized colliding beams are used to enhance the signal production cross-section. Low tan β and equal Higgs masses regime is chosen in favor of Hadronic decay of Z boson and H → b b. Different signal scenarios are selected and event generation is performed for each process separately. The W , Z bosons, and top quark backgrounds are also analyzed. Signal significance is computed at each Higgs mass hypothesis for three signal processes. After a comprehensive study, we did not find sizeable amount of signal events on top of the background but still, signal significance is found larger than 1 without taking into account the detector effects and systematics. The maximum calculated value of signal significance is observed in the range of 150 ≤ m H ≤ 250 GeV for Zhh while for ZHH the range is 175 ≤ m H ≤ 200 GeV at 1000 f b −1 and 175 ≤ m H ≤ 225 GeV region at 2500 f b −1 . Similarly, for ZAA process, the significance is highest at m A = 175 GeV for both 1000 and 2500 f b −1 .