Abstract
A search is reported for massive resonances decaying into a quark and a vector boson (W or Z), or two vector bosons (WW, WZ, or ZZ). The analysis is performed on an inclusive sample of multijet events corresponding to an integrated luminosity of 19.7 inverse femtobarns, collected in proton-proton collisions at a centre-of-mass energy of 8 TeV with the CMS detector at the LHC. The search uses novel jet-substructure identification techniques that provide sensitivity to the presence of highly boosted vector bosons decaying into a pair of quarks. Exclusion limits are set at a confidence level of 95% on the production of: (i) excited quark resonances q* decaying to qW and qZ for masses less than 3.2 TeV and 2.9 TeV, respectively, (ii) a Randall-Sundrum graviton G[RS] decaying into WW for masses below 1.2 TeV, and (iii) a heavy partner of the W boson W' decaying into WZ for masses less than 1.7 TeV. For the first time mass limits are set on W' to WZ and G[RS] to WW in the all-jets final state. The mass limits on q* to qW, q* to qZ, W' to WZ, G[RS] to WW are the most stringent to date. A model with a "bulk" graviton G[Bulk] that decays into WW or ZZ bosons is also studied.
Highlights
A search is reported for massive resonances decaying into a quark and a vector boson (W or Z), or two vector bosons (WW, WZ, or ZZ)
The analysis is performed on an inclusive sample of multijet events corresponding to an integrated luminosity of 19.7 fb−1, collected in proton-proton collisions at a centre-of-mass energy of 8 TeV with the CMS detector at the LHC
Exclusion limits are set at a confidence level of 95% on the production of: (i) excited quark resonances q∗ decaying to qW and qZ for masses less than 3.2 TeV and 2.9 TeV, respectively, (ii) a Randall-Sundrum graviton GRS decaying into WW for masses below 1.2 TeV, and (iii) a heavy partner of the W boson W decaying into WZ for masses less than 1.7 TeV
Summary
In this study the event selection, in the online trigger as well as offline, utilizes a global view of the event involving information combined from the individual subdetectors. Events with jets originating from calorimeter noise are rejected, requiring that a fraction of the jet energy is detected in the tracking system Following this selection, the jet reconstruction efficiencies (estimated from simulation) are larger than 99.9%, and contribute negligibly to the systematic uncertainties for signal events. Differences are observed in signal distributions predicted with herwig++ (for GRS), with pythia (q∗, W ), and with jhugen/pythia (Gbulk), for the mass mj of pruned jets and for τ21 These differences arise from unlike polarization of the vector bosons in the various signals models and from differences between herwig++ and pythia in the modelling of the showering and hadronization of partons. We estimate from simulation that backgrounds from tt, W+jets and Z+jets events with the vector bosons decaying into quark final states contribute less than 2% of total background
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