Physicists at the Large Hadron Collider (LHC) have made a groundbreaking discovery, observing evidence of antihyperhelium-4, a bound state of two antiprotons, an antineutron, and an antilambda. This finding marks the first time such a heavy antimatter hypernucleus has been detected at the LHC, with a significance of 3.5 standard deviations.
The ALICE collaboration used machine-learning techniques to analyze data from lead-lead collisions in 2018, searching for signals of hyperhydrogen-4 and hyperhelium-4 as well as their antimatter partners. They identified candidates by looking for the nucleus and its decay products.
The researchers measured the production yields and masses of both hypernuclei, finding that they are compatible with current world-average values. The results agree closely with predictions from a statistical hadronisation model, which describes the formation of hadrons and nuclei in heavy-ion collisions.
This discovery confirms that the model can also describe the production of hypernuclei, compact objects with sizes of around 2 femtometres. Additionally, the antiparticle-to-particle yield ratios for both hypernuclei agree with unity within experimental uncertainties, consistent with previous observations of equal matter-antimatter production at LHC energies.
This finding adds to ongoing research into the matter-antimatter imbalance in the Universe and provides valuable insights into the formation of quark-gluon plasma and exotic hypernuclei.
Source: https://home.cern/news/news/physics/alice-finds-first-ever-evidence-antimatter-partner-hyperhelium-4