Abstract

This paper presents a study of the production of WW or WZ boson pairs, with one W boson decaying to enu or mu nu and one W or Z boson decaying hadronically. The analysis uses 20.2~text{ fb }^{-1} of sqrt{s} =8~text {TeV}pp collision data, collected by the ATLAS detector at the Large Hadron Collider. Cross-sections for WW / WZ production are measured in high-p_{mathrm {T}} fiducial regions defined close to the experimental event selection. The cross-section is measured for the case where the hadronically decaying boson is reconstructed as two resolved jets, and the case where it is reconstructed as a single jet. The transverse momentum distribution of the hadronically decaying boson is used to search for new physics. Observations are consistent with the Standard Model predictions, and 95% confidence intervals are calculated for parameters describing anomalous triple gauge-boson couplings.

Highlights

  • Background estimationThe methods for estimating the expected background yields and kinematic distributions are described

  • Systematic uncertainties in the V + jets shape are estimated by varying the Monte Carlo (MC) event generator used (Sherpa compared to Alpgen+Pythia)

  • Uncertainties in the signal shapes and in the Dfid parameter due to variations of the signal model are computed by varying the renormalization and factorization scales by factors of 2 and 0.5, and by comparing the nominal MC@next-to-leading order (NLO) signal samples to alternative samples generated with Sherpa and Powheg +Pythia 8

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Summary

Analysis overview

Measurements of W V → νqq production are performed using either two small-R jets or a single large-R jet to reconstruct the hadronically decaying V boson For both channels, the leptonically decaying W boson is reconstructed by requiring the presence of a lepton (electron or muon) and missing transverse momentum. The signal events peak near the W/Z mass in these distributions, while the shape of the dominant W + jets background is smoothly falling. In both channels, the signal is extracted from a fit to the dis-. An initial hardwarebased trigger stage is followed by two software-based triggers, which reduce the final event rate to about 400 Hz

Data and Monte Carlo samples
Event reconstruction
Event selection
The transverse mass is defined as mT
Background estimation
Background
Cross-section extraction
Systematic uncertainties
10 Cross-section results
Z cW W W
12 Conclusion
Findings
Methods
Full Text
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