Search for VH and Technicolor Production in the qqbb Final State Using the RunII D0 Detector

Abstract

A search for dijet resonance production in a four-jet all-hadronic final state from the DO detector at Fermilab's Tevatron is presented. The data set, acquired at a ppbar center-of-mass energy of sqrt{s}=1.96 TeV, contains primarily multijet events and represents approximately 1 fb-1 of data. The cross section limits for associated Higgs production and Technicolor processes are determined through a background subtraction method using data to estimate the background. This four-jet channel is potentially very powerful, but is extremely challenging due to the large multijet background from QCD processes. Background rejection is performed by utilizing b-tagging, pre-selection cuts, a multi-variate boosted decision tree discriminant, and the correlated information contained in the M(bb) and M(jj) dijet invariant masses. The search for VH (WH+ZH) processes yields a 95% confidence level observed upper limit of 20.4 pb on the VH cross section for a Higgs mass of 115 GeV/c2. Additionally, a 95% confidence level observed upper limit of 16.7 pb was set for a Higgs boson mass of 125 GeV/c2 and 24.6 pb was set for a Higgs boson mass of 135 GeV/c2. The same data set was used to place limits on the Technicolor process ρTC→ WπTC where the technirho mass was fixed to 240 GeV/c2. For a technipion mass of 115 GeV/c2 we find a 95% confidence level observed upper limit on the cross section of 49 pb. The technipion masses of 125 GeV/c2 and 140 GeV/c2, the 95% confidence level observed upper limits are 57 pb and 71 pb, respectively.