The LHC created the heaviest antimatter particle on Earth – antihyperhelium-4

CERN reported that the ALICE scientific collaboration has for the first time discovered today’s heaviest exotic particles and their antimatter antipodes. Scientists have long been concerned with the problem of why there is a lot of matter in our world and almost no antimatter. Matter and antimatter were supposed to appear in equal proportions, but at some point after the Big Bang, something went wrong and antimatter almost disappeared from the Universe. They are looking for the answer in the LHC.

Image source: Janik Ditzel / ALICE collaboration

Earlier this year, the STAR collaboration at the Relativistic Heavy Ion Collider (RHIC) observed antihyperhydrogen-4. These are bound states of an antiproton, two antineutrons and an anti-lambda. All this is antimatter, experiments with which make it possible to understand the reasons for the imbalance of matter and antimatter in the Universe. The ALICE collaboration at CERN’s Large Hadron Collider (LHC) decided to go further and find the next heaviest atom and its antimatter version.

It is noteworthy that artificial intelligence helped detect traces of new particles. Scientists took data from experiments in 2018, where two beams of lead ions collided at the LHC. The program was for the first time able to identify signs of antihyperhelium-4 – antimatter in relation to the exotic hyperhelium-4. The antihyperhelium-4 atom consists of two antiprotons, an antineutron and an antilambda. The result has a value of 3.5 standard deviations (sigma) and also represents the first evidence of the heaviest antimatter hypernucleus ever observed at the LHC.

Also in this analysis, an antihyperhydrogen-4 nucleus was discovered with a standard deviation of 4.5 sigma. ALICE employees confirmed the discovery of their colleagues and were able to measure the yields and masses of both hypernuclei. It must be said that hypernuclei were first discovered about 70 years ago during the decay of cosmic particles in the atmosphere. Scientists can only envy the cosmic energy of such particles, the level of which is hardly possible to replicate in earthly laboratories.

By the way, antihyperhelium-4 appeared at the LHC with a collision energy of 5.02 TeV (teraelectronvolt), which simply pales in comparison to the record registrations of cosmic particles with energies of hundreds of exaelectronvolts, and this is a difference of up to eight orders of magnitude.

The yield of antihyperhelium-4 recorded by scientists is equal to unity, which means that it is formed equally with atoms of hyperhelium-4. Scientists have again become convinced that there should be equal amounts of matter and antimatter in the Universe. We are looking further for the cause of the asymmetry.