Abstract
Dijet events produced in LHC proton--proton collisions at a center-of-mass energy $\sqrt{s}=8$ TeV are studied with the ATLAS detector using the full 2012 data set, with an integrated luminosity of 20.3 fb$^{-1}$. Dijet masses up to about 4.5 TeV are probed. No resonance-like features are observed in the dijet mass spectrum. Limits on the cross section times acceptance are set at the 95% credibility level for various hypotheses of new phenomena in terms of mass or energy scale, as appropriate. This analysis excludes excited quarks with a mass below 4.09 TeV, color-octet scalars with a mass below 2.72 TeV, heavy $W'$ bosons with a mass below 2.45 TeV, chiral ${W^\ast}$ bosons with a mass below 1.75 TeV, and quantum black holes with six extra space-time dimensions with threshold mass below 5.82 TeV.
Highlights
This paper describes the search for new phenomena (NP)
For models with a larger width after detector effects, the limit that best matches their width should be used. These results may be used to set limits on NP models beyond those considered in the current studies, as described in detail in Appendix A
In the 2012 running of the ATLAS experiment at the Large Hadron Collider (LHC), the collision energy was raised from 7 TeV to 8 TeV, accompanied by a more than fourfold increase in integrated luminosity
Summary
In the two-jet (dijet) invariant mass spectrum in the full 2012 data set delivered by the Large Hadron Collider (LHC) at CERN, and collected with the ATLAS detector. High-transverse-momentum (high-pT) dijet events are produced copiously by QCD processes, and can reach the highest mass scales accessible in LHC pp collisions. The QCD processes, along with a subpercent admixture of additional Standard Model (SM) processes, create a smooth rapidly falling spectrum in mjj. If the resonance width is sufficiently narrow, these NP signals would appear as local excesses (bumps) in the dijet mass spectrum over the smooth SM background. Studies searching for excesses in dijet mass spectra have been performed in all previous collider experiments, including CDF and D0 at the Tevatron [1,2,3,4]. The current dijet search sets limits on new generic resonances whose intrinsic width is convolved with effects due to parton distribution functions (PDFs), parton shower, nonperturbative effects and detector resolution
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