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University of Cambridge’s Cavendish Laboratory finds more evidence that Standard Model of physics needs revising



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Further evidence that the current theory of fundamental physics needs revising was revealed yesterday (Tuesday), following measurements by scientists at the University of Cambridge’s Cavendish Laboratory.

Results from the LHCb experiment at CERN near Geneva cannot be explained by the Standard Model, they said.

The LHCb experiment at CERN. Picture: CERN (45646694)
The LHCb experiment at CERN. Picture: CERN (45646694)

The Standard Model describes all known particles that make up the universe and the forces through which they interact. It had passed all experimental tests.

But in March, the experiment found evidence of particles breaking one of its core principles. Now further measurements have found similar effects.

Physicists have long known that the Standard Model is not complete. It does not include the force of gravity, nor account for how matter was produced during the Big Bang. It also contains no particle that could explain dark matter – which astronomy has shown is five times more abundant than all the things that make up the visible world.

The search for new particles and forces has led physicists to study beauty quarks – exotic cousins of the ‘up and down’ quarks that make up the nucleus of every atom.

These beauty quarks survive on average for just a trillionth of a second before they transform or decay into other particles.

But billions of them are produced every year by CERN’s giant particle accelerator, the Large Hadron Collider, and are recorded by a purpose-built detector called LHCb.

In March, physicists at LHCb released evidence that beauty quarks were decaying into particles called muons less often than to their lighter cousins, electrons, which was impossible to explain in the Standard Model, which treats them equally.

There was only a one in a 1,000 chance this was a statistical fluke.

Cambridge physicists re-examining the decay of beauty quarks recorded similar findings, although this time there was just over a two chance of it being a statistical fluke.

“The fact that we’ve seen the same effect as our colleagues did in March certainly boosts the chances that we might genuinely be on the brink of discovering something new,” said Dr Harry Cliff from the Cavendish Laboratory.

“It’s great to shed a little more light on the puzzle.”

The most likely explanation for the measurements is thought to be that a new force that pulls on electrons and muons with different strengths is interfering with the decay.

“The excitement at the Large Hadron Collider is growing just as the upgraded LHCb detector is about to be switched on and further data collected that will provide the necessary statistics to either claim or refute a major discovery,” added Professor Val Gibson, also from the Cavendish Laboratory.

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