Search for exotic decays of the Higgs boson into $b\bar{b}$ and missing transverse momentum in $pp$ collisions at $\sqrt{s}=13$ TeV with the ATLAS detector

Abstract

A search for the exotic decay of the Higgs boson ($H$) into a $b\bar{b}$ resonance plus missing transverse momentum is described. The search is performed with the ATLAS detector at the Large Hadron Collider using 139 ${\mathrm{fb}}^{-1}$ of $pp$ collisions at $\sqrt{s}=13$ TeV. The search targets events from $ZH$ production in an NMSSM scenario where $H\to {\tilde{\chi }}_2^0{\tilde{\chi }}_1^0$, with ${\tilde{\chi }}_2^0\to a{\tilde{\chi }}_1^0$, where $a$ is a light pseudoscalar Higgs boson and ${\tilde{\chi }}_{1,2}^0$ are the two lightest neutralinos. The decay of the $a$ boson into a pair of $b$-quarks results in a peak in the dijet invariant mass distribution. The final-state signature consists of two leptons, two or more jets, at least one of which is identified as originating from a $b$-quark, and missing transverse momentum. Observations are consistent with Standard Model expectations and upper limits are set on the product of cross section times branching ratio for a three-dimensional scan of the masses of the ${\tilde{\chi }}_2^0$, ${\tilde{\chi }}_1^0$ and $a$ boson.

arXiv commentComments: 38 pages in total, author list starting on page 22, 4 figures, 2 tables, published in JHEP. All figures, including auxiliary figures are available at http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HDBS-2018-07/

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