Search for Higgs boson pair production in the $b\bar{b}b\bar{b}$ final state from $pp$ collisions at $\sqrt{s}=8$ TeV with the ATLAS detector

Abstract

A search for Higgs boson pair production $pp\to hh$ is performed with 19.5 fb${}^{-1}$ of proton--proton collision data at $\sqrt{s}=$ 8 TeV, which were recorded by the ATLAS detector at the Large Hadron Collider in 2012. The decay products of each Higgs boson are reconstructed as a high-momentum $b\bar{b}$ system with either a pair of small-radius jets or a single large-radius jet, the latter exploiting jet substructure techniques and associated $b$-tagged track-jets. No evidence for resonant or non-resonant Higgs boson pair production is observed. The data are interpreted in the context of the Randall--Sundrum model with a warped extra dimension as well as the two-Higgs-doublet model. An upper limit on the cross-section for $pp\to G_{\mathrm{KK}}^{\ast }\to hh\to b\bar{b}b\bar{b}$ of 3.2 (2.3) fb is set for a Kaluza--Klein graviton $G_{\mathrm{KK}}^{\ast }$ mass of 1.0 (1.5) TeV, at the 95\% confidence level. The search for non-resonant Standard Model $hh$ production sets an observed 95\% confidence level upper limit on the production cross-section $\sigma (pp\to hh\to b\bar{b}b\bar{b})$ of 202 fb, compared to a SM prediction of $\sigma (pp\to hh\to b\bar{b}b\bar{b})=3.6\pm 0.5$ fb.

32 pages plus author list + cover pages (49 pages total), 18 figures, 9 tables, submitted to EPJC. All figures including auxiliary figures are available at http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/EXOT-2014-11/