ATLAS

Abstract:

A search for a heavy Higgs boson in the H → WW and H → ZZ decay channels is reported. The search is based upon proton-proton collision data samples corresponding to an integrated luminosity of up to 5.1 fb−1 at s√=7 TeV and up to 19.7fb−1 at s√=8 TeV, recorded by the CMS experiment at the CERN LHC. Several final states of the H → WW and H → ZZ decays are analyzed. The combined upper limit at the 95% confidence level on the product of the cross section and branching fraction exclude a Higgs boson with standard model-like couplings and decays in the range 145 < m H < 1000 GeV. We also interpret the results in the context of an electroweak singlet extension of the standard model.

Abstract:

This article reports on a search for dark matter pair production in association with a Higgs boson decaying to a pair of bottom quarks, using data from $20.3 fb^{-1}$ of $pp$ collisions at a center-of-mass energy of 8 TeV collected by the ATLAS detector at the LHC. The decay of the Higgs boson is reconstructed as a high-momentum $b\bar{b}$ system with either a pair of small-radius jets, or a single large-radius jet with substructure. The observed data are found to be consistent with the expected Standard Model backgrounds. Model-independent upper limits are placed on the visible cross-sections for events with a Higgs boson decaying into $b\bar{b}$ and large missing transverse momentum with thresholds ranging from 150 GeV to 400 GeV. Results are interpreted using a simplified model with a $Z^\prime$ gauge boson decaying into different Higgs bosons predicted in a two-Higgs-doublet model, of which the heavy pseudoscalar Higgs decays into a pair of dark matter particles. Exclusion limits are also presented for the mass scales of various effective field theory operators that describe the interaction between dark matter particles and the Higgs boson.