Abstract
The ATLAS detector at the Large Hadron Collider is used to search for high-mass resonances decaying to dielectron or dimuon final states. Results are presented from an analysis of proton-proton (pp) collisions at a center-of-mass energy of 8 TeV corresponding to an integrated luminosity of 20.3 fb-1 in the dielectron channel and 20.5 fb-1 in the dimuon channel. A narrow resonance with Standard Model Z couplings to fermions is excluded at 95% confidence level for masses less than 2.79 TeV in the dielectron channel, 2.53 TeV in the dimuon channel, and 2.90 TeV in the two channels combined. Limits on other model interpretations are also presented, including a grand-unification model based on the E6 gauge group, Z* bosons, Minimal Z' Models, a spin-2 graviton excitation from Randall-Sundrum models, quantum black holes and a Minimal Walking Technicolor model with a composite Higgs boson.
Highlights
The current energy frontier can be explored in the invariant mass spectrum of dielectron or dimuon pairs via a search for new massive resonances at the Large Hadron Collider (LHC)
Among these are grand-unification models, which are motivated by gauge unification or a restoration of the left-right symmetry violated by the weak interaction
In the class of models based on the E6 gauge group, this unified symmetry group can break to the Standard Model (SM) in a number of different ways [2]
Summary
The current energy frontier can be explored in the invariant mass spectrum of dielectron or dimuon pairs via a search for new massive resonances at the Large Hadron Collider (LHC). The dilepton invariant mass (mll) line shape is examined for a localized excess of events corresponding to a new resonance, where ll corresponds to either the dielectron or dimuon final state. This is done using signal and background templates that provide the expected yield of events in bins of mll. Interference effects, where they occur, are not expected to significantly alter the line shape and are not considered The exception to this is the class of minimal Z0 models described in Sec. II, for which large coupling strengths, and larger widths, are considered. Boson with mass less than 1.79 TeV (1.97 TeV) at 95% C.L. [17], while the CMS experiment excludes a Z0ψ boson with mass less than 2.26 TeV at 95% C.L. [18]
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