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Di-Higgs final states augMT2ed -- selecting $hh$ events at the high luminosity LHC

Higgs boson self-interactions can be investigated via di-Higgs ($pp\to hh+X$) production at the LHC. With a small ${\cal{O}}(30)$ fb Standard Model production cross section, and a large $t\bar t$ background, this measurement has been considered challenging, even at a luminosity-upgraded LHC. We demonstrate that by using simple kinematic bounding variables, of the sort already employed in existing LHC searches, the dominant $t\bar t$ background can be largely eliminated. Simulations of the signal and the dominant background demonstrate the prospect for measurement of the di-Higgs production cross section at the 30% level using 3/ab of integrated luminosity at a high-luminosity LHC. This corresponds to a Higgs self-coupling determination with 60% accuracy in the $b\bar b τ^+τ^-$ mode, with potential for further improvements from e.g. subjet technologies and from additional di-Higgs decay channels.