Study of $$WW\gamma $$ W W γ and $$WZ\gamma $$ W Z γ production in $$pp$$ p p collisions at $$\sqrt{s} = {8} \,{\text {TeV}}$$ s = 8 TeV and search for anomalous quartic gauge couplings with the ATLAS experiment (2017)

This paper presents a study of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>W</mml:mi> <mml:mi>W</mml:mi> <mml:mi>γ</mml:mi></mml:mrow> </mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>W</mml:mi> <mml:mi>Z</mml:mi> <mml:mi>γ</mml:mi></mml:mrow> </mml:math> triboson production using events from proton-proton collisions at a centre-of-mass energy of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow><mml:msqrt><mml:mi>s</mml:mi></mml:msqrt> <mml:mo>=</mml:mo> <mml:mtext>8</mml:mtext> <mml:mspace></mml:mspace> <mml:mtext>TeV</mml:mtext></mml:mrow> </mml:math> recorded with the ATLAS detector at the LHC and corresponding to an integrated luminosity of 20.2 fb <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msup><mml:mrow></mml:mrow> <mml:mrow><mml:mo>-</mml:mo> <mml:mn>1</mml:mn></mml:mrow> </mml:msup> </mml:math> . The <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>W</mml:mi> <mml:mi>W</mml:mi> <mml:mi>γ</mml:mi></mml:mrow> </mml:math> production cross-section is determined using a final state containing an electron, a muon, a photon, and neutrinos ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>e</mml:mi> <mml:mi>ν</mml:mi> <mml:mi>μ</mml:mi> <mml:mi>ν</mml:mi> <mml:mi>γ</mml:mi></mml:mrow> </mml:math> ). Upper limits on the production cross-section of the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>e</mml:mi> <mml:mi>ν</mml:mi> <mml:mi>μ</mml:mi> <mml:mi>ν</mml:mi> <mml:mi>γ</mml:mi></mml:mrow> </mml:math> final state and the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>W</mml:mi> <mml:mi>W</mml:mi> <mml:mi>γ</mml:mi></mml:mrow> </mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>W</mml:mi> <mml:mi>Z</mml:mi> <mml:mi>γ</mml:mi></mml:mrow> </mml:math> final states containing an electron or a muon, two jets, a photon, and a neutrino ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>e</mml:mi> <mml:mi>ν</mml:mi> <mml:mi>j</mml:mi> <mml:mi>j</mml:mi> <mml:mi>γ</mml:mi></mml:mrow> </mml:math> or <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>μ</mml:mi> <mml:mi>ν</mml:mi> <mml:mi>j</mml:mi> <mml:mi>j</mml:mi> <mml:mi>γ</mml:mi></mml:mrow> </mml:math> ) are also derived. The results are compared to the cross-sections predicted by the Standard Model at next-to-leading order in the strong-coupling constant. In addition, upper limits on the production cross-sections are derived in a fiducial region optimised for a search for new physics beyond the Standard Model. The results are interpreted in the context of anomalous quartic gauge couplings using an effective field theory. Confidence intervals at 95% confidence level are derived for the 14 coupling coefficients to which <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>W</mml:mi> <mml:mi>W</mml:mi> <mml:mi>γ</mml:mi></mml:mrow> </mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>W</mml:mi> <mml:mi>Z</mml:mi> <mml:mi>γ</mml:mi></mml:mrow> </mml:math> production are sensitive.