Hints of exotic dark matter particles could be hiding in LHC data

Axions, theoretical particles that have been at the forefront of physicists’ pursuit for decades, are expected to be responsible for dark matter. Interestingly, researchers are now exploring the data from previous particle collider experiments to identify exotic particles that could be similar to axions—without the need for new experimental setups.

Particle colliders like the Large Hadron Collider (LHC) based at CERN, near Geneva, Switzerland, are crucial for discovering new particles. These machines accelerate protons and ions, causing them to collide at high energy, while scientists analyze the debris from these collisions. Recent work by Gustavo Gil da Silveira and colleagues at CERN proposed an intriguing concept: if a proton or ion releases a new particle while accelerating, could this phenomenon be detectable? Their analysis indicates that under specific circumstances, it is indeed possible.

Originally theorized in the 1970s, axions were proposed to solve a major dilemma in physics: the imbalance between the existence of matter and antimatter. Despite extensive searches for axions yielding no direct evidence, these efforts opened avenues for the exploration of related particles. Given their low mass, axion-like particles may exhibit similarities to massless photons, which have successfully been studied within the LHC environment.

When protons or ions accelerate to tremendous velocities, they can radiate photons as they near each other. Surpassing this, the research team modeled scenarios involving axion-like particles, predicting that collisions between protons and lead ions could provide insight into axion interactions. In fact, a specific collision event conducted in 2016 at the LHC, involving protons and lead ions, might contain valuable clues about previously overlooked axion-like particles.

According to Lucian Harland-Lang from University College London, this approach represents a novel and intriguing pathway for investigating potential undiscovered particles. However, it may present challenges, as such collision events are rare, necessitating thorough analysis to rule out background processes that could mimic signals of interest. Accessing older LHC data also poses difficulties, especially since updates to software can affect usability.

Da Silveira remains optimistic, suggesting that ongoing LHC experiments could enhance the likelihood of detecting such signals. “We could adjust the detectors specifically to capture this signal,” he notes.

While identifying axion-like particles wouldn’t definitively confirm the existence of axions, it would expand our understanding of particle physics, leading to further inquiries about how these new particles might interact with known ones and their potential role in the fabric of dark matter in our universe.

Journal Reference: Physical Review Letters, in press