Observation of 𝑉� 𝑉� 𝑍� production at √𝑠� = 13 TeV with the ATLAS detector

Abstract

A search for the production of three massive vector bosons, SQUARE ROOT 𝑉 𝑉 𝑍(𝑉 = 𝑊,𝑍), in proton-proton collisions at𝑠 = 13 TeV is performed using data with an integrated luminosity of 140 fb-1 recorded by the ATLAS detectorat the Large Hadron Collider. Events produced in the leptonic final states 𝑊𝑊𝑍 RIGHTWARDS ARROW𝓁𝜈𝓁𝜈𝓁𝓁 (𝓁 = 𝑒,𝜇), 𝑊𝑍𝑍 RIGHTWARDS ARROW𝓁𝜈𝓁𝓁𝓁𝓁, 𝑍𝑍𝑍 RIGHTWARDS ARROW 𝓁𝓁𝓁𝓁𝓁𝓁, and the semileptonic final states 𝑊𝑊𝑍 RIGHTWARDS ARROW 𝑞𝑞𝓁𝜈𝓁𝓁 and 𝑊𝑍𝑍 RIGHTWARDS ARROW 𝓁𝜈𝑞𝑞𝓁𝓁, areanalysed. The measured cross section for the 𝑝𝑝RIGHTWARDS ARROW 𝑉 𝑉 𝑍 process is 660+93-90(stat.)+88-81(syst.) fb, and the observed(expected) significance is 6.4 (4.7) standard deviations, representing the observation of 𝑉 𝑉 𝑍 production.In addition, the measured cross section for the 𝑝𝑝 RIGHTWARDS ARROW 𝑊𝑊𝑍 process is 442 +- 94(stat.)+60-52(syst.) fb, and theobserved (expected) significance is 4.4 (3.6) standard deviations, representing evidence of 𝑊𝑊𝑍 production.The measured cross sections are consistent with the Standard Model predictions. Constraints on physics beyondthe Standard Model are also derived in the effective field theory framework by setting limits on Wilson coefficientsfor dimension-8 operators describing anomalous quartic gauge boson couplings.