Abstract

A search for pair production of neutral color-octet weak-triplet scalar particles (Theta) is performed in processes where one Theta decays to a pair of b quark jets and the other to a Z boson plus a jet, with the Z boson decaying to a pair of electrons or muons. The search is performed with data collected by the CMS experiment at the CERN LHC corresponding to an integrated luminosity of 19.7 inverse femtobarns of proton-proton collisions at sqrt(s) = 8 TeV. The number of observed events is found to be in agreement with the standard model predictions. The 95% confidence level upper limit on the product of the cross section and branching fraction is obtained as a function of the Theta mass. The 95% confidence level lower bounds on the Theta mass are found to be 623 and 426 GeV, for two different octo-triplet theoretical scenarios. These are the first direct experimental bounds on particles predicted by the octo-triplet model.

Highlights

  • Background onlyZ + jet mass shape b jet pair mass shape NormalizationDiboson cross section Signal only Initial state radiation (ISR)Integrated luminosityAbove 120 GeV, an uncertainty is assigned that varies from 5 to 20%, depending on the pT

  • A search for pair production of neutral color-octet weak-triplet scalar particles (Θ0) is performed in processes where one Θ0 decays to a pair of b quark jets and the other to a Z boson plus a jet, with the Z boson decaying to a pair of electrons or muons

  • With no existing constraints on the ratio of Θ0 decays to quarks versus those decaying to Zg, we have studied a final state that includes both decay modes

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Summary

CMS detector

The central feature of the CMS apparatus is a superconducting solenoid of 6 m internal diameter, providing a magnetic field of 3.8 T. Within the solenoid volume are a silicon pixel and strip tracker, a lead tungstate crystal electromagnetic calorimeter, and a brass and scintillator hadron calorimeter, each composed of a barrel and two endcap sections. Muons are measured in gas-ionization detectors embedded in the steel flux-return yoke outside the solenoid. Extensive forward calorimetry complements the coverage provided by the barrel and endcap detectors. A more detailed description of the CMS detector, together with a definition of the coordinate system used and the relevant kinematic variables, can be found in ref. A more detailed description of the CMS detector, together with a definition of the coordinate system used and the relevant kinematic variables, can be found in ref. [23]

Event selection
Backgrounds
Multijet events
Systematic uncertainties
Background only
Results
Background

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