Abstract

A search is conducted for new resonances decaying into a W W or W Z boson pair, where one W boson decays leptonically and the other W or Z boson decays hadronically. It is based on proton-proton collision data with an integrated luminosity of 36.1 fb−1 collected with the ATLAS detector at the Large Hadron Collider at a centre-of-mass energy of sqrt{s}=13 TeV in 2015 and 2016. The search is sensitive to diboson resonance production via vector-boson fusion as well as quark-antiquark annihilation and gluon-gluon fusion mechanisms. No significant excess of events is observed with respect to the Standard Model backgrounds. Several benchmark models are used to interpret the results. Limits on the production cross section are set for a new narrow scalar resonance, a new heavy vector-boson and a spin-2 Kaluza-Klein graviton.

Highlights

  • Background estimationSimulation studies indicate that the dominant background sources are with jets (W +jets) and ttevents

  • Studies using simulated events show that 77%–87% of the selected gluon-gluon fusion (ggF)/qqand vector-boson fusion (VBF) category events are from ttproduction and the rest are from single-top, V +jets or diboson production, for both the merged and the resolved event topologies

  • The likelihood is defined as the product of the Poisson likelihoods for all signal and control regions for a given production mechanism category and channel (W W or W Z), simultaneously for the electron and muon channels

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Summary

ATLAS detector

The ATLAS detector [22] is a general-purpose particle detector used to investigate a broad range of physics processes It includes an inner detector (ID) surrounded by a superconducting solenoid, electromagnetic (EM) and hadronic calorimeters and a muon spectrometer (MS) inside a system of toroidal magnets. The ID consists of a silicon pixel detector including a newly installed innermost layer called the insertable B-layer [23], a silicon microstrip detector and a straw-tube tracker. It is immersed in a 2 T axial magnetic field and provides precision tracking of charged particles with pseudorapidity1 |η| < 2.5. The ATLAS detector has a two-level trigger system that is based on custom hardware followed by a software trigger to reduce the selected event rate to approximately 1 kHz for offline analysis [24]

Signal and background simulation
Event reconstruction
Trigger and event selection
Background estimation
Systematic uncertainties
Results
Conclusions
MC statistical uncertainty 5 tt: scale

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