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LHC team's 'unfinished business'

British scientists are gearing up to complete "unfinished business" with the universe after the world's biggest atom smashing machine restarts this year.

The Large Hadron Collider (LHC) particle accelerator has been off-line for two years undergoing a major upgrade.

When the massive machine straddling the French and Swiss borders recommences operations in the spring it will generate subatomic collisions with energies of 13 tera-electron volts (TeV).

This is more than triple the power available when LHC scientists made their momentous Higgs boson discovery in 2012.

Researchers had been searching for the elusive boson, which is said to give other particles mass, since its existence was first theorised in 1964 by British physicist Peter Higgs.

Beam energies are directly related to particle discoveries because of the way energy converts into mass, as described in Albert Einstein's famous equation E=MC squared. (E stands for energy, M for mass and C the speed of light).

Higher energies mean that more particles, and particles with greater mass, can be created. Accelerators are also used to probe the nature of fundamental particles and forces, and higher energy gives them more resolution.

Three years of LHC experiments are planned which are expected to provide important new information about the Higgs boson and answers to big questions in physics.

One key riddle is why there is so little antimatter in the universe. At the time of the Big Bang that gave birth to the universe 13.8 billion years ago, there should have been equal amounts of ordinary matter and antimatter, which has electrons and protons with a reversed electric charge.

The new improved LHC may also unveil the true nature of dark matter, the mysterious invisible "stuff" that makes up more than a quarter of the mass-energy of the universe and holds galaxies together.

Scientists also hope to make a start testing the theory of Supersymmetry, which predicts that every known particle has a corresponding and unknown "super-particle" partner.

There are four main LHC experiments, Alice, LHCb, CMS and Atlas, each of which is centred on one of the huge detectors arranged around its 27 kilometre (17 mile) long beam tunnel ring.

Professor Tara Shears, who leads the University of Liverpool LHCb group, said: "We have unfinished business with understanding the universe.

"We want to see what the new data shows us about antimatter, and why there's so little in the universe. We want to chase the hints we've seen in previous measurements, whose behaviour didn't quite match our expectations, in case these hints turn into discoveries.

"We've spent the shut-down readying and improving the LHCb detectors so that we can explore this new data with precision."

Dr Victoria Martin, from Edinburgh University, a member of the Atlas team, said: "Using data from LHC Run One we discovered the Higgs boson particle. However only a limited number of Higgs particles were produced and it has not yet been possible to test every prediction made by Peter Higgs and others.

"The higher energy and more frequent proton collisions in Run Two will allow us to investigate the Higgs particle in much more detail. Higher energy may also allow the mysterious 'dark matter' observed in galaxies to be made and studied in the lab for the first time."

On December 9 the magnets on one section of the LHC ring were successfully powered to the level needed for a single particle beam to reach 6.5 TeV.

The goal this year will be to run two beams of proton particles in opposite directions to produce 13 TeV collisions.

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