Measurement of W+W − production in association with one jet in proton–proton collisions at √s = 8 TeV with the ATLAS detector

Abstract

The production of W boson pairs in association with one jet in pp collisions at √s = 8 TeV is studied using data corresponding to an integrated luminosity of 20.3 fb−1 collected by the ATLAS detector during 2012 at the CERN Large Hadron Collider. The cross section is measured in a fiducial phase-space region defined by the presence of exactly one electron and one muon, missing transverse momentum and exactly one jet with a transverse momentum above 25 GeV and a pseudorapidity of |η| < 4.5. The leptons are required to have opposite electric charge and to pass transverse momentum and pseudorapidity requirements. The fiducial cross section is found to be <math><msubsup is="true"><mrow is="true"><mi is="true">σ</mi></mrow><mrow is="true"><mi is="true">W</mi><mi is="true">W</mi></mrow><mrow is="true"><mtext is="true">fid,1-jet</mtext></mrow></msubsup><mo is="true">=</mo><mn is="true">136</mn><mo is="true">±</mo><mn is="true">6</mn><mrow is="true"><mo stretchy="true" is="true">(</mo><mtext is="true">stat</mtext><mo stretchy="true" is="true">)</mo></mrow><mo is="true">±</mo><mn is="true">14</mn><mrow is="true"><mo stretchy="true" is="true">(</mo><mtext is="true">syst</mtext><mo stretchy="true" is="true">)</mo></mrow><mo is="true">±</mo><mn is="true">3</mn><mrow is="true"><mo stretchy="true" is="true">(</mo><mtext is="true">lumi</mtext><mo stretchy="true" is="true">)</mo></mrow><mtext is="true"></mtext><mtext is="true">fb</mtext></math>. In combination with a previous measurement restricted to leptonic final states with no associated jets, the fiducial cross section of W W production with zero or one jet is measured to be <math><msubsup is="true"><mrow is="true"><mi is="true">σ</mi></mrow><mrow is="true"><mi is="true">W</mi><mi is="true">W</mi></mrow><mrow is="true"><mtext is="true">fid</mtext><mo is="true">,</mo><mo is="true">≤</mo><mn is="true">1</mn><mtext is="true">-jet</mtext></mrow></msubsup><mo is="true">=</mo><mn is="true">511</mn><mo is="true">±</mo><mn is="true">9</mn><mrow is="true"><mo stretchy="true" is="true">(</mo><mtext is="true">stat</mtext><mo stretchy="true" is="true">)</mo></mrow><mo is="true">±</mo><mn is="true">26</mn><mrow is="true"><mo stretchy="true" is="true">(</mo><mtext is="true">syst</mtext><mo stretchy="true" is="true">)</mo></mrow><mo is="true">±</mo><mn is="true">10</mn><mrow is="true"><mo stretchy="true" is="true">(</mo><mtext is="true">lumi</mtext><mo stretchy="true" is="true">)</mo></mrow><mtext is="true"></mtext><mtext is="true">fb</mtext></math>. The ratio of fiducial cross sections in final states with one and zero jets is determined to be 0.36 ± 0.05. Finally, a total cross section extrapolated from the fiducial measurement of W W production with zero or one associated jet is reported. The measurements are compared to theoretical predictions and found in good agreement.