Professor Peter Higgs stands in front of a photograph of the Large Hadron Collider at the Science Museum's 'Collider' exhibition in London, 2013. Source: Getty Images

A model of the Large Hadron Collider (LHC) tunnel is seen in the CERN (European Organisation for Nuclear Research) visitors' centre June 16, 2008 in Geneva-Meyrin, Switzerland. Source: Getty Images

Scientists at the European Organization for Nuclear Research, or CERN, on Sunday shot two particle beams through the Large Hadron Collider’s 27-km tunnel, beneath the Swiss-French border near Geneva.

The collider was instrumental in the discovery of the Higgs boson, a subatomic particle that had long been theorised but never confirmed until 2013.

Scientists are promising nearly twice the energy and more violent particle crashes this time around. They hope to see all sorts of new physics, including a first ever glimpse of dark matter, during the collider’s second three-year run.

The magnet core of the world's largest superconducting solenoid magnet at the European Organization for Nuclear Research (CERN)'s Large Hadron Collider (LHC) in Geneva Switzerland. Source: AP

CERN said the restart went smoothly and faster than expected. However it will be a while yet before the accelerator is working at full speed and particle crashes start.

“It will take us about six weeks to two months to establish the first stable collisions for the experiments, because we have to commission all the instruments, all the systems one by one,” said Joerg Wenninger, the accelerator’s co-ordinator of operations.

Dark matter — and its cousin, dark energy — make up most of the universe, but scientists haven’t been able to see them yet, so researchers are looking for them in high-energy crashes, in orbit in a special experiment on the international space station, and in a deep underground mine.

CERN spent about $150 million on the upgrade, opening the massive machine every 20 meters (66 feet), checking magnets and improving connections.

AP