ATLAS Collaboration Advances Search for Dark Matter Particles

Researchers from the ATLAS Collaboration have made significant strides in the search for dark matter, focusing their efforts on the elusive dark sector of the universe. This hidden realm may hold the key to understanding dark matter, which remains one of the most profound mysteries in modern physics. The team has been investigating potential new particles that could provide insights into this enigmatic field.

In various theoretical frameworks, dark matter is thought to consist of dark quarks, which are fundamental particles that could form long-lived dark mesons through a process called hadronization. These mesons, composed of dark quarks and antiquarks, would eventually decay into ordinary particles. The decay process would manifest as unusual “emerging jets”—bursts of particles that originate from displaced vertices rather than the primary collision point.

To explore this hypothesis, the ATLAS team utilized 51.8 fb−1 of proton–proton collision data collected at 13.6 TeV during the period from 2022 to 2023. They specifically searched for events featuring two emerging jets and examined two production mechanisms: a vector mediator, known as Z′, produced in the s-channel, and a scalar mediator, referred to as Φ, exchanged in the t-channel.

Innovative Analytical Approaches

The analysis employed two complementary strategies. The first was a cut-based method that focused on high-level jet observables, including selections based on track, vertex, and jet substructure. This approach facilitates straightforward reinterpretation for various theoretical models. The second strategy involved advanced machine learning techniques, utilizing a per-jet tagger based on a transformer architecture trained on low-level tracking variables. This innovative approach aimed to enhance the discrimination between emerging jets and those predicted by the Standard Model, thereby maximizing sensitivity for the specific models under investigation.

Although no excess signal of emerging jets was found, the search yielded the first direct limits on emerging-jet production via the Z′ mediator and established the first constraints on t-channel Φ production. Depending on the model assumptions, the results excluded possible Z′ masses up to approximately 2.5 TeV and Φ masses up to about 1.35 TeV. These findings significantly narrow the parameter space for potential dark sector particles, representing a crucial advancement in the ongoing quest to understand the nature of dark matter.

Future Implications for Dark Matter Research

The work conducted by the ATLAS Collaboration is part of a broader program to investigate dark quantum chromodynamics, which seeks to uncover the fundamental interactions governing dark matter. By refining the search parameters and establishing stringent limits on theoretical models, this research paves the way for future explorations into the dark sector.

As scientists continue to grapple with the complexities of dark matter, these findings not only advance our understanding but also enhance the strategies that will be employed in subsequent searches. The implications of this research extend beyond theoretical physics, potentially influencing our comprehension of the universe and its underlying forces.

For more detailed insights, refer to the full article titled “Search for emerging jets in pp collisions at √s = 13.6 TeV with the ATLAS experiment,” published in 2025 Rep. Prog. Phys. 88 097801.