Sensitivity to triple Higgs couplings via di-Higgs production in the 2HDM at the (HL-)LHC

Abstract

Abstract An important task of the LHC is the investigation of the Higgs-boson sector. Of particular interest is the reconstruction of the Higgs potential, i.e. the measurement of the Higgs self-couplings. Based on previous analyses, within the 2-Higgs-Doublet Model (2HDM) type I, we analyze several two-dimensional benchmark planes that are over large parts in agreement with all theoretical and experimental constraints. For these planes we evaluate di-Higgs production cross sections at the (HL-)LHC with a center-of-mass energy of $$14 \,\, \textrm{TeV}$$ 14 TeV at next-to-leading order in the heavy top-quark limit with the code HPAIR. We investigate in particular the process $$gg \rightarrow hh$$ g g → h h , with h being the Higgs boson discovered at the LHC with a mass of about $$125 \,\, \textrm{GeV}$$ 125 GeV . The top box diagram of the loop-mediated gluon fusion process into Higgs pairs interferes with the s-channel exchange of the two $${\mathcal{C}\mathcal{P}}$$ C P -even 2HDM Higgs bosons h and H. The latter two involve the triple Higgs couplings (THCs) $$\lambda _{hhh}$$ λ hhh and $$\lambda _{hhH}$$ λ hhH , respectively, possibly making them accessible at the HL-LHC. Depending on the size of the involved top-Yukawa and THCs as well as on the mass of H, the contribution of the s-channel H diagram can be dominating or be highly suppressed. We find regions of the allowed parameter space in which the di-Higgs production cross section can differ by many standard deviations from its SM prediction, indicating possible access to deviations in $$\lambda _{hhh}$$ λ hhh from the SM value $$\lambda _{\textrm{SM}}$$ λ SM and/or contributions involving $$\lambda _{hhH}$$ λ hhH . The sensitivity to the beyond-the-SM (BSM) THC $$\lambda _{hhH}$$ λ hhH is further analyzed employing the $$m_{hh}$$ m hh distributions. We demonstrate how a possible measurement of $$\lambda _{hhH}$$ λ hhH depends on the various experimental uncertainties. Depending on the underlying parameter space, the HL-LHC may have the option not only to detect BSM THCs, but also to provide a first rough measurement of their sizes.