New observations of light atomic nuclei formation from high-energy collisions could shed light on the mystery of dark matter.
At the Large Hadron Collider (LHC), collisions occur at temperatures over one hundred thousand times hotter than the center of the Sun. Surprisingly, light nuclei and their antimatter counterparts emerge from this fiery environment intact. For years, scientists have wondered how this is possible. Now, the ALICE collaboration has provided vital evidence published in Nature.
ALICE researchers focused on deuterons (a proton and a neutron) and antideuterons (an antiproton and an antineutron) formed during high-energy proton collisions. They discovered that around 90% of these light nuclei did not come directly from the collisions. Instead, they were formed through the nuclear fusion of particles emerging from the collisions, with one particle originating from the decay of a short-lived particle.
Marco van Leeuwen, a spokesperson for the ALICE experiment, noted, “These results represent a milestone for the field. They provide essential input for the next generation of theoretical models.” This discovery not only solves a lingering question in nuclear physics but also could impact fields like astrophysics and cosmology. Light nuclei are produced during interactions between cosmic rays and the interstellar medium. Importantly, they may also be linked to dark matter processes that fill the Universe.
Understanding how light nuclei form helps physicists better analyze cosmic-ray data and look for potential dark matter signals. The ALICE findings reveal that many light nuclei aren’t formed in a single energetic event. Instead, they arise from a series of decays and fusions occurring as the system cools down.
The ALICE collaboration reached these conclusions by studying deuterons generated from high-energy proton collisions. They measured the momenta of deuterons alongside pions—particles made up of a quark-antiquark pair. A correlation between the momenta of these particles indicated that the pion and a part of the deuteron came from a short-lived particle’s decay.
This short-lived particle, the delta resonance, decays incredibly quickly—approximately one trillionth of a trillionth of a second—creating a pion and either a proton or neutron. The resulting nucleon can then fuse with nearby nucleons to create light nuclei like deuterons in a less extreme environment, giving them a better chance to survive. Both particles and antiparticles follow the same formation process, suggesting a universal principle at play.
“This discovery highlights the ALICE experiment’s unique capabilities to study the strong nuclear force under extreme conditions,” said Alexander Philipp Kalweit, ALICE’s physics coordinator.
These insights not only deepen our understanding of nuclear physics but also open the door to exploring the cosmic phenomena linked to dark matter. As scientists continue to probe the intricacies of our universe, the role of light nuclei may become even more significant in deciphering its mysteries.
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physics, CERN, Large Hadron Collider, LHC, high-energy physics, particles, science
