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

A bstract A search for the exotic decay of the Higgs boson ( H ) into a b $ \overline{b} $ b ¯ resonance plus missing transverse momentum is described. The search is performed with the ATLAS detector at the Large Hadron Collider using 139 fb − 1 of pp collisions at $ \sqrt{s} $ s = 13 TeV. The search targets events from ZH production in an NMSSM scenario where H → $ {\overset{\sim }{\chi}}_2^0{\overset{\sim }{\chi}}_1^0 $ χ ~ 2 0 χ ~ 1 0 , with $ {\overset{\sim }{\chi}}_2^0 $ χ ~ 2 0 → $ a{\overset{\sim }{\chi}}_1^0 $ a χ ~ 1 0 , where a is a light pseudoscalar Higgs boson and $ {\overset{\sim }{\chi}}_{1,2}^0 $ χ ~ 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 $ {\overset{\sim }{\chi}}_2^0 $ χ ~ 2 0 , $ {\overset{\sim }{\chi}}_1^0 $ χ ~ 1 0 and a boson.