Projected sensitivity of searches for Higgs boson pair production in final states with light leptons, taus, and photons with the ATLAS detector at the HL-LHC

A projection of the sensitivity to non-resonant Higgs boson pair production in the bbZZ, 4V (V = W or Z), VV, 4, VV and decay channels from LHC Run 2 to the High Luminosity LHC with the upgraded ATLAS detector is presented. Sensitivities are projected assuming a centre-of-mass energy of 14\, TeV for integrated luminosities ranging from 1000 to 3000\, fb^-1 and for a variety of systematic uncertainty scenarios. Under the baseline (statistical only) extrapolation scenario for an integrated luminosity of 3000\, fb^-1, a combined signal significance of 1. 0 (1. 2) is expected, while the 95\% confidence-level upper limit on the HH signal strength is found to be 2. 1 (1. 7). The modifier of the trilinear Higgs boson self-coupling, _, is correspondingly constrained to the interval -0. 8, 5. 6 (-0. 6, 5. 5) at the 95\% confidence level.