Researchers affiliated with the ATLAS Collaboration at the Large Hadron Collider, operated by CERN, have reported the inaugural detection of VVZ production, a seldom-occurring confluence of three substantial vector bosons.
A three-vector-boson event recorded by ATLAS, with one W boson decaying to an electron and a neutrino, one W boson decaying to a muon and a neutrino, and a Z boson decaying to two muons; muons are shown by red lines, the electron by a green line, and ‘missing energy’ from the neutrino by a dashed white line. Image credit: ATLAS / CERN.
As the fundamental carriers of the weak nuclear force, W and Z bosons hold a pivotal position within the Standard Model of particle physics.
Meticulous quantification of multi-boson production mechanisms serves as an exceptionally rigorous validation of the Standard Model and possesses the potential to illuminate novel physical phenomena.
“The genesis of three vector (V) bosons represents an exceedingly infrequent event at the LHC,” stated Dr. Fabio Cerutti, ATLAS physics coordinator.
“Its measured occurrence provides critical insights into the intricate interactions between multiple bosons, which are intrinsically linked to the fundamental symmetries underpinning the Standard Model.”
“This endeavor constitutes a formidable instrument for uncovering hitherto unknown physics, such as the existence of new, undiscovered particles that are too massive to be directly generated within the LHC’s operational parameters.”
The ATLAS investigative group achieved the observation of VVZ production, registering a statistical significance of 6.4 standard deviations, thereby exceeding the requisite five standard deviation benchmark for definitive observation claims.
This landmark observation builds upon prior findings from both the ATLAS and CMS collaborations, including CMS’s documentation of VVV production and ATLAS’s earlier confirmation of WWW production.
Given their status as some of the most substantial known particles, W and Z bosons are capable of undergoing decay through a vast array of distinct pathways.
Within the scope of this recent investigation, the ATLAS physicists concentrated their efforts on precisely seven decay modalities exhibiting the highest probability of discovery.
Further refinement of these specific decay channels was accomplished through the application of a sophisticated machine-learning paradigm known as boosted decision trees, wherein algorithms were meticulously calibrated for each individual channel to effectively discern the targeted signal.
Through the synergistic integration of these various decay channels, the research team successfully ascertained the existence of VVZ production and concurrently established constraints on the potential influence of novel physics phenomena on the observed signal.
“The resultant limitations unequivocally corroborate the established integrity of the Standard Model and align harmoniously with preceding results pertaining to the generation of three vector bosons,” the researchers commented.
“As we embark on the analysis of augmented datasets derived from the LHC’s third operational phase and the forthcoming High-Luminosity upgrade, our measurements characterizing the production of three vector bosons will undergo further enhancement, thereby deepening our comprehension of these fundamental constituents and their integral role within the cosmos.”
The scientific dissemination of the team’s groundbreaking findings is slated for publication in the esteemed journal Physics Letters B.
_____
ATLAS Collaboration. 2025. Observation of VVZ production at s√=13 TeV with the ATLAS detector. Phys. Lett. B, in press; arXiv: 2412.15123
