Scientists at CERN’s Large Hadron Collider (LHC) have directly observed the mysterious dominance of matter over antimatter within subatomic particles called baryons for the first time. Baryons constitute most observable matter in the universe. This asymmetry, predicted by the Standard Model of particle physics, had previously been detected in other particles but never before in baryons. The breakthrough, achieved by the LHCb experiment, is published in *Nature* and involved significant contributions from Italian researchers across multiple National Institute for Nuclear Physics (INFN) centers.
According to theory, the Big Bang produced equal amounts of matter and antimatter. Yet, matter prevailed, creating our universe. “We live in a universe of matter,” stated Vincenzo Vagnoni, INFN Bologna researcher and head of the LHCb collaboration, to ANSA. “If symmetry had been perfect, matter and antimatter would have annihilated each other, leaving only radiation – and the universe as we know it would never have formed.”
The observed asymmetry is minuscule. Immediately after the Big Bang, nearly all matter and antimatter particles annihilated each other, evidenced by the cosmic background radiation. However, a tiny fraction of matter particles survived for unknown reasons. “The problem is that the asymmetry predicted by the Standard Model isn’t large enough to explain what happened in the universe’s first moments,” Vagnoni emphasized. “This implies something beyond the Standard Model – new particles, new interactions we haven’t observed yet. Phenomena with a larger matter-antimatter asymmetry must exist. Our current measurements might hide signs of new physics that could explain this asymmetry, but we cannot confirm it yet.”
While asymmetry was first observed in 1964, detecting it in baryons proved far more challenging due to its extremely small size and the need for powerful instruments to produce sufficient baryons and analyze results. “It required many baryons and a powerful detector like LHCb to collect the thousands of events needed to spot this tiny asymmetry,” Vagnoni explained. He noted that LHCb has so far collected only one-thirtieth of the total data expected by the experiment’s end. “We are still at the beginning, even though last year we obtained more data than the previous 15 years combined. There’s much still to understand. We hope the LHC’s energy will be sufficient to pinpoint the discrepancies with the Standard Model we know must exist.”
Riproduzione riservata © Copyright ANSA