Plate Nº 88 · recorded November 13, 2026
PhysicsReported finding
LHCb Finds No Crack in Physics' Symmetry — Yet
LHCb measured a matter–antimatter asymmetry of one to two per thousand B meson decays, consistent with the Standard Model but narrowing where new physics could hide.
By Elena Vasquez4 min read768 words
In brief
- LHCb analyzed proton–proton collision data from 2016–2018, published in Physical Review Letters (2026), DOI 10.1103/ljtv-y278.
- The measured matter–antimatter difference was about 1–2 cases per thousand decays, within measurement uncertainty.
- Any unknown process causing an asymmetry above roughly 2% in these decays would almost certainly have been detected.
- Beauty mesons oscillate between matter and antimatter states several trillion times per second.
- The team included physicists from Warwick, Manchester, Oxford, TU Dortmund and IFJ PAN in Cracow.
The LHCb collaboration has measured a matter–antimatter asymmetry of roughly one to two cases per thousand decays — a difference so small it's consistent with the Standard Model and offers no evidence of new physics. The result, published in Physical Review Letters, comes from an exceptionally thorough analysis of proton–proton collision data collected between 2016 and 2018 at the Large Hadron Collider.
The team behind the measurement includes physicists from the universities of Warwick, Manchester and Oxford in the U.K., TU Dortmund University in Germany, and the Institute of Nuclear Physics of the Polish Academy of Sciences (IFJ PAN) in Cracow. Over the past decade, LHC scientists have hunted for differences between matter and antimatter particles produced in these collisions.
Why does antimatter matter?
The universe shouldn't exist — at least not according to our current understanding. Cosmological models suggest the Big Bang produced equal amounts of matter and antimatter. When a particle meets its antiparticle, both vanish into energy through a process called annihilation. Yet ordinary matter clearly dominates today's cosmos, meaning matter and antimatter cannot be — and never were — perfect mirror images of each other.
"In many physical processes, simultaneously replacing all particles with their antiparticles and inverting all spatial coordinates leaves the laws governing these phenomena unchanged. This principle is known as charge-parity symmetry, or CP symmetry," explains Dr. Agnieszka Dziurda of IFJ PAN. "We have been searching for processes that violate this symmetry in the decays of mesons containing beauty and strange quarks and antiquarks."
The Standard Model — the theoretical framework developed in the 1970s that describes elementary particles and their interactions — holds that matter consists of fermions: quarks (down, up, strange, charm, beauty and top) and leptons (electrons, muons, tau leptons and their neutrinos). Every matter particle has a corresponding antiparticle. Physicists have observed CP violation in certain decay processes before, but those known asymmetries are far too small to explain why matter won.
Why study a decay predicted to be symmetric?
The researchers analyzed decays of Bₛ⁰ mesons into lighter particles. The Standard Model predicts no asymmetry at all in this channel — which is precisely the point.
"Interestingly, we chose to investigate a process in which the Standard Model predicts no asymmetry at all. So why study it at all?" asks Dziurda. "Because if an asymmetry were nevertheless observed, it could be a signal that previously unknown physics was at work."
She adds that current theoretical predictions for certain beauty-meson decay channels differ significantly from experimental values. That gap could stem from theoretical effects not yet fully accounted for in calculations — but it could also point to physics beyond the Standard Model, and nobody can rule that out yet.
Beauty mesons offered another advantage: they oscillate extremely rapidly between matter states (a strange quark paired with a beauty antiquark) and antimatter states (a beauty quark paired with a strange antiquark). An earlier LHCb measurement showed these oscillations can occur several trillion times per second. That speed let the team run the analysis without determining each meson's initial state.
How did they rule out the detector?
Detector asymmetries posed the biggest challenge. Positively and negatively charged particles curve in opposite directions in the detector's magnetic field, and detection efficiencies vary across the detector — effects that can mimic a real asymmetry even when particles and antiparticles decay at identical rates.
"We had to make sure that any asymmetry observed in the data, however small, was not caused by the detector itself," says Dziurda. "This was a crucial aspect of the entire analysis because, given the precision of our measurement, detector-related effects could have been of the same magnitude as the asymmetry we were looking for."
The team used extensive calibration samples, computer simulations and regular reversals of the magnetic field direction, then corrected for detection-efficiency differences in the final result.
What does the null result change?
The observed difference of one to two per thousand decays came with an uncertainty larger than the effect itself, so it matches Standard Model predictions. It doesn't solve the antimatter mystery, but it narrows the hunt: any unknown process causing an asymmetry greater than about 2% in these decays would almost certainly have been seen.
Future work with larger datasets from the upgraded LHCb detector will probe subtler effects. If a new source of CP violation is hiding there, physicists now know better where — and how — to look.
Publication details: R. Aaij et al., First Measurement of the Decay-Time-Integrated CP Asymmetry in Bₛ⁰ → Ds−π+ Decays, Physical Review Letters (2026). DOI: 10.1103/ljtv-y278.
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Correspondent covering money, funding and market shifts around general science news at SciBeat.
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