Combination of searches for Higgs boson pairs in pp collisions at s=13TeV with the ATLAS detector

Abstract

This letter presents a combination of searches for Higgs boson pair production using up to 36.1fb−1of proton–proton collision data at a centre-of-mass energy √s=13TeVrecorded with the ATLAS detector at the LHC. The combination is performed using six analyses searching for Higgs boson pairs decaying into the b¯bb¯ b, b¯bW+W−, b¯ bτ+τ−, W+W−W+W−, b¯ bγγand W+W−γγfinal states. Results are presented for non-resonant and resonant Higgs boson pair production modes. No statistically significant excess in data above the Standard Model predictions is found. The combined observed (expected) limit at 95% confidence level on the non-resonant Higgs boson pair production cross-section is 6.9(10) times the predicted Standard Model cross-section. Limits are also set on the ratio (κλ) of the Higgs boson self-coupling to its Standard Model value. This ratio is constrained at 95% confidence level in observation (expectation) to −5.0 <κλ<12.0(−5.8 <κλ<12.0). In addition, limits are set on the production of narrow scalar resonances and spin-2 Kaluza–Klein Randall–Sundrum gravitons. Exclusion regions are also provided in the parameter space of the habemus Minimal Supersymmetric Standard Model and the Electroweak Singlet Model.