New tests back concept for particle physics: CERN

PARIS, France - Tests at the world's biggest collider have provided the most exhaustive confirmation to date of the Standard Model, a four-decade-old conceptual framework for fundamental particles, CERN said on Friday.

Physicists at two giant underground laboratories straddling the French-Swiss border have given the most accurate measurement yet of a change in a particle called a Bs.

New measurements showed that out of every billion Bs particles, only a handful decay into smaller particles called muon, and they do so in pairs, the European Organisation for Nuclear Research (CERN) said.

"Because the process is so rare, it is an extremely sensitive probe for new physics beyond the Standard Model," it said in a statement issued in Geneva.

"Any divergence from the Standard Model prediction would be a clear sign of something new."

CERN's Large Hadron Collider (LHC) smashes sub-atomic particles together in a circular tunnel, where four laboratories use ultra-sensitive monitors to record the debris that tumbles from the collision.

The Standard Model, conceived in the 1970s, is the chief vehicle for understanding the basic particles and forces that make up the Universe.

In a historic discovery last year, the LHC uncovered a particle believed to be the elusive Higgs Boson, which explains mass.

Still missing from the Standard Model are explanations for gravity and the enigmatic stuff called dark matter and dark energy, which account for most of the cosmos and whose existence is inferred from their impact on ordinary matter.

The Bs tests were made by the LHC's CMS and LHCb labs.

"It's precisely for measurements like this that LHCb was built," said the lab's spokesman, Pierluigi Campana. "This result shows that we're really putting the Standard Model to the most stringent test yet at LHC energies, and so far it's coming through with flying colours."

The research was presented on Friday at a European conference on high-energy physics in Stockholm, CERN said.

In other work put forward in Stockholm, European and Japanese scientists confirmed two-year-old evidence that an elusive elementary particle, the neutrino, transits from one state to the other - from a muon neutrino to an electron neutrino.

Physicists beamed muon neutrinos across nearly 300 kilometres (185 miles) in Japan. They found that the beam, on its arrival, had more electron neutrinos in it than at the start, proving that a transformation had taken place.