Abstract
The production of $W$ boson pairs in proton-proton collisions at $\sqrt{s}=$ 8 TeV is studied using data corresponding to 20.3 fb$^{-1}$ of integrated luminosity collected by the ATLAS detector during 2012 at the CERN Large Hadron Collider. The $W$ bosons are reconstructed using their leptonic decays into electrons or muons and neutrinos. Events with reconstructed jets are not included in the candidate event sample. A total of 6636 $WW$ candidate events are observed. Measurements are performed in fiducial regions closely approximating the detector acceptance. The integrated measurement is corrected for all acceptance effects and for the $W$ branching fractions to leptons in order to obtain the total $WW$ production cross section, which is found to be 71.1$\pm1.1$(stat)$^{+5.7}_{-5.0}$(syst)$\pm1.4$ pb. This agrees with the next-to-next-to-leading-order Standard Model prediction of 63.2$^{+1.6}_{-1.4}$(scale)$\pm1.2$(PDF) pb. Fiducial differential cross sections are measured as a function of each of six kinematic variables. The distribution of the transverse momentum of the leading lepton is used to set limits on anomalous triple-gauge-boson couplings.
Highlights
The measurement of the production of pairs of electroweak gauge bosons plays a central role in tests of the Standard Model (SM) and in searches for new physics at the TeV scale [1]
Photos [29] is used to model the radiation of photons, and AU2 [30] and AUET2 [31] are used as the parameter tunes for the underlying event in the Powheg+Pythia and the Herwig+Jimmy samples, respectively
Jets containing b-hadrons are identified within the central region of the detector, |ηjet| < 2.5, using a multivariate approach based on track impact-parameter significance, secondary vertex reconstruction and other tracking variables described in refs. [65, 66]
Summary
The measurement of the production of pairs of electroweak gauge bosons plays a central role in tests of the Standard Model (SM) and in searches for new physics at the TeV scale [1]. Fixed-order calculations may fail to describe effects that arise from restrictions imposed on the phase space of the measurement. Several calculations including resummation effects up to next-to-next-to-leading logarithms (NNLL) have appeared recently in the literature [4,5,6,7] Both the fixed-order and resummed predictions are compared to the measurements in this paper, except for ref. Measurements of differential cross sections are presented and limits on anomalous triple-gauge-boson couplings are reported
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