On the reinterpretation of non-resonant searches for Higgs boson pairs

Abstract: The detection of production of a pair of Higgs bosons before the end of LHC operation would be clear evidence of New Physics (NP). As searches for non-resonant production of Higgs pairs are being designed it is of particular importance to be able to conveniently present current experimental results in terms of limits in the most 'model-independent' fashion possible. In this article we provide an analytic parametrization of the {\it differential} Higgs-pair production at the LHC in the effective field theory (EFT) extension of the SM. It results from a fit to the theory prediction for the $gg \to hh$ cross section at the 13\,TeV at the LHC. Subsequently the resulting formula is used for a reweighing technique that allows to recast exclusion bounds from ATLAS and CMS HH$\to\gamma\gamma\,b\bar{b}$ searches to any point of the considered EFT parameter space. We demonstrate with a fast simulation of the LHC detectors that with this approach it is possible to cover the continuously of the EFT parameter space, taking correctly into account the efficiencies of signal selections, without the necessity of rerunning a large number of full detector simulations. Finally, the resulting exclusion bounds are confronted to several explicit models such as setups with additional scalars, including 2HDM, vector-like fermions, and minimal composite Higgs models, mapped to the EFT.