The Higgs decay width can be constrained by exploiting interference effects of the pp -> H->γγ signal with the pp->γγ continuum
background, which yields a width-dependent shift of the observed Higgs mass peak. I review a study in which my collaborators and I investigate the HL-LHC reach of an analysis that determines the reference mass from the di-photon final state at high transverse momenta, where the shift is less pronounced. As an alternative strategy, we also propose a yet more powerful technique based on a direct fit to the distorted m_γγ line shape. Both approaches employ particle-level predictions calculated with the Monte-Carlo event generator Sherpa, and I will take time to introduce some of the relevant concepts.
