The Large Hadron Collider was built to look inside the atom. A team working on one of its detectors has now published a measurement of what happens roughly 100 billion times deeper than that.
The analysis, from the LHCb experiment at CERN and led by Dr Harry Cliff at the University of Cambridge, concerns the beauty quark — a short-lived particle produced in high-energy collisions that survives about 1.5 trillionths of a second before decaying. By studying the debris of those decays, the team measured beauty-quark interactions at a scale of about a billion-trillionth of a metre, or 10⁻²¹ m. An atom is roughly 10⁻¹⁰ m across, which is where the "100 billion times smaller" figure comes from.
Some of the researchers have taken to calling that regime the zeptoverse, after the zepto- prefix (10⁻²¹). "We're knocking on the door of this zeptoverse," Cliff told BBC News, describing the measurement as a ringside seat on the behaviour of possible new particles.
What has actually been achieved is a measurement of interaction scale, not the discovery of a new particle. The interest is theoretical: many extensions of the Standard Model place new physics — including candidates tied to dark matter — at very short distances, where they would subtly change how beauty quarks interact and decay. Probing at 10⁻²¹ m is how you begin testing those ideas, and the way to do more of it is more data.
That is where the politics arrives. The 28 countries collaborating on LHCb have agreed a £150 million upgrade to the detector that would increase the frequency of these decays tenfold. Earlier this year, UK Research and Innovation withdrew the UK's share of that money, as part of cuts across particle physics and astronomy that also hit Jodrell Bank's Lovell telescope.
"With that we can probe inside the zeptoverse and see what's waiting," Cliff said of the upgrade. Professor Tim Gershon, who leads the LHCb collaboration, told the BBC that without the funding the UK's full involvement in the research would be in doubt, and warned that the bigger long-term cost is the loss of training for young researchers.
Dr Mary Richardson-Slipper, a member of the team that made the measurement, said she is looking at jobs abroad. "I love being here in the UK, but I am looking at jobs abroad because that seems to be where there are more opportunities at the moment," she said, adding that many colleagues in fundamental physics have already moved.
UKRI says it remains CERN's second-largest funder at around £175 million a year, and that it took independent advice before redirecting money toward infrastructure in clean energy, medical imaging and cultural heritage. The physicist and broadcaster Brian Cox, who was not part of the analysis, called the result important and the withdrawal "extraordinary", warning it would damage Britain's research programme and reputation.
For now the measurement stands on its own: the smallest distances probed at the LHC, published in the same year that one of the countries which made the case for going further began stepping back from the next step.
