CERN finds highly significant hint of physics beyond the Standard Model

Monday 01 - 10:20

By: Dakir Madiha

CERN finds highly significant hint of physics beyond the Standard Model

Physicists working at the Large Hadron Collider at CERN have produced what may be among the strongest evidence yet that the Standard Model of particle physics is incomplete, publishing results showing that rare subatomic particle decays known as penguin decays behave in ways the current theory cannot explain. The findings arrive as the LHC prepares to shut down for a major upgrade, a project now clouded by the United Kingdom's decision to withdraw a substantial portion of its funding commitment.

The results, accepted for publication in Physical Review Letters, come from the LHCb experiment and concern the decay of particles called B mesons into kaons and pairs of muons. Researchers found that the angles at which the decay products appear diverge from Standard Model predictions at a level of four standard deviations, meaning there is only a one-in-16,000 chance that random statistical fluctuation could produce such a result if the Standard Model were correct. Evidence for the anomaly has been accumulating quietly since 2015, with the latest analysis drawing on approximately 650 billion decays collected across two LHC run periods between 2011 and 2018. A particle physicist at the University of Edinburgh and member of the LHCb collaboration told the journal Nature that one possible explanation would be the existence of a hypothetical particle called a Z-prime, which would act as a virtual intermediary in the decay process.

Although the result does not reach the five-sigma threshold physicists require to declare a discovery, researchers emphasized that the accumulated evidence is difficult to dismiss. The team acknowledged that despite their enthusiasm, open theoretical questions remain that prevent them from definitively claiming to have observed physics beyond the Standard Model. The caution reflects longstanding practice in high-energy physics, where several four-sigma anomalies in past decades ultimately dissolved when larger datasets were analyzed.

The timing adds a layer of complexity to the significance of the findings. The LHC is scheduled to shut down on June 29 for its High-Luminosity upgrade, which will increase the number of particle collisions tenfold and allow far greater statistical precision. However, the British government announced in early 2025 the cancellation of more than 250 million pounds in planned physical infrastructure funding, including contributions to the LHCb upgrade at CERN. The decision by UK Research and Innovation means the LHCb experiment will likely cease operations in 2033 without its planned next-generation detector. The cuts form part of broader reductions totaling 162 million pounds over four years by the Science and Technology Facilities Council, with the government redirecting resources toward artificial intelligence and life sciences. British physicists now face the prospect of playing a reduced role in the very experiments that could confirm or refute some of the most intriguing hints in contemporary particle physics.