Higgs Boson Self-Coupling at High Energy $gamma gamma$ Collider

We analyzed the double production and the triple self-coupling of the standard model Higgs boson at future $gamma gamma$ collider energies, with the reactions $gammagamma rightarrow f bar f HH$ $(f=b, t)$. We evaluated the total cross section for $fbar fHH$ and calculated the total number of events considering the complete set of Feynman diagrams at tree-level and for different values of the triple coupling $kappalambda_{HHH}$. We have also analyzed the sensitivity for the considered reaction and we show the results as 95% C.L. regions in the $kappa-M_H$ plane for different values of the center of mass energy and different levels of background. The numerical computation was done for the energies which are expected to be available at a possible Future Linear $gammagamma$ Collider with a center-of-mass energy 500-3000 $GeV$ and luminosities of 1 and $5 ab^{-1}$. We found that the number of events for the process $gammagamma rightarrow t bar t HH$, taking into account the decay products of both $t$ and $H$, is small but enough to obtain information on the triple Higgs boson self-coupling in a independent way, complementing other studies on the triple vertex.

Neutral Higgs Boson Pair-Production and Trilinear Self-Couplings in the MSSM at ILC and CLIC Energies

We study pair-production as well as the triple self-couplings of the neutral Higgs bosons of the Minimal Supersymmetric Standard Model (MSSM) at the Future International Linear $e^{+}e^{-}$ Collider (ILC) and Compact Linear Collider (CLIC). The analysis is based on the reactions $e^{+}e^{-}to b bar b h_ih_i, t bar t h_ih_i$ with $h_i=h, H, A$. We evaluate the total cross-section for both $bbar bh_ih_i$, $tbar th_ih_i$ and calculate the total number of events considering the complete set of Feynman diagrams at tree-level. We vary the triple couplings $kappalambda_{hhh}$, $kappalambda_{Hhh}$, $kappalambda_{hAA}$, $kappalambda_{HAA}$, $kappalambda_{hHH}$ and $kappalambda_{HHH}$ within the range $kappa=-1$ and +2. The numerical computation is done for the energies expected at the ILC with a center-of-mass energy 500, 1000, 1600 $GeV$ and a luminosity 1000 $fb^{-1}$. The channels $e^{+}e^{-}to b bar b h_ih_i$ and $e^{+}e^{-}to t bar t h_ih_i$ are also discussed to a center-of-mass energy of 3 $TeV$ and luminosities of 1000 $fb^{-1}$ and 5000 $fb^{-1}$.

The Triple Higgs Boson Self-Coupling at Future Linear e+e- Colliders Energies: ILC and CLIC

We analyzed the triple Higgs boson self-coupling at future $e^{+}e^{-}$ colliders energies, with the reactions $e^{+}e^{-}to b bar b HH, t bar t HH$. We evaluate the total cross-sections for both $bbar bHH$ and $tbar tHH$, and calculate the total number of events considering the complete set of Feynman diagrams at tree-level. We vary the triple coupling $kappalambda_{3H}$ within the range $kappa=-1$ and +2. The numerical computation is done for the energies expected to be available at a possible Future Linear $e^{+}e^{-}$ Collider with a center-of-mass energy $800, 1000, 1500$ $GeV$ and a luminosity 1000 $fb^{-1}$. Our analysis is also extended to a center-of-mass energy 3 $TeV$ and luminosities of 1000 $fb^{-1}$ and 5000 $fb^{-1}$. We found that for the process $e^{+}e^{-}to b bar b HH$, the complete calculation differs only by 3% from the approximate calculation $e^{+}e^{-}to ZHH(Zto bbar b)$, while for the process $e^{+}e^{-}to t bar tHH$, the expected number of events, considering the decay products of both $t$ and $H$, is not enough to obtain an accurate determination of the triple Higgs boson self-coupling.