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), VVττ, 4τ, γγ VV and γγττ 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 1.0σ (1.2σ) 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, κ_λ, is correspondingly constrained to the interval [-0.8, 5.6] ([-0.6, 5.5]) at the 95% confidence level.