Search for non-resonant Higgs boson pair production in the 2b+2l+ETmiss final state in <i>pp</i> collisions at √s=13 TeV with the ATLAS detector

Abstract

<p>A search for non-resonant Higgs boson pair (<em>HH</em>) production is presented, in which one of the Higgs bosons decays to a <em>b</em>-quark pair () and the other decays to <em>WW</em>^*, <em>ZZ</em>^*, or <em>τ</em>⁺<em>τ</em>^<em>−</em>, with in each case a final state with <em>ℓ</em>⁺<em>ℓ</em>^<em>−</em>+ neutrinos (<em>ℓ</em> = <em>e, μ</em>). The analysis targets separately the gluon-gluon fusion and vector boson fusion production modes. Data recorded by the ATLAS detector in proton-proton collisions at a centre-of-mass energy of 13 TeV at the Large Hadron Collider, corresponding to an integrated luminosity of 140 fb^{<em>−</em>1}, are used in this analysis. Events are selected to have exactly two <em>b</em>-tagged jets and two leptons with opposite electric charge and missing transverse momentum in the final state. These events are classified using multivariate analysis algorithms to separate the <em>HH</em> events from other Standard Model processes. No evidence of the signal is found. The observed (expected) upper limit on the cross-section for non-resonant Higgs boson pair production is determined to be 9.7 (16.2) times the Standard Model prediction at 95% confidence level. The Higgs boson self-interaction coupling parameter <em>κ</em>_<em>λ</em> and the quadrilinear coupling parameter <em>κ</em>_2<em>V</em> are each separately constrained by this analysis to be within the ranges [<em>−</em>6<em>.</em>2<em>,</em> 13<em>.</em>3] and [<em>−</em>0<em>.</em>17<em>,</em> 2<em>.</em>4], respectively, at 95% confidence level, when all other parameters are fixed.<br></p>