Large Hadron Collider produces historic particle collisions

Washington, August 26 : On of the Large Hadron Collider's (LHC's) four giant particle detectors has gathered its first authentic data, as well as marking the first time particle tracks have been reconstructed from a man-made event generated by the collider.

The LHC, located under the Franco-Swiss border near Geneva, Switzerland, is the world's largest and the highest-energy particle accelerator.

Some 15 years in construction, the LHC is based at the European particle facility CERN, and is due to start its proper experimental work on September 10.

On Friday, August 22, physicists tracked the debris produced by protons that had struck a block of concrete during a test of the collider's beam-injection system.

The LHC's particle detectors have been recording hits from cosmic rays for several months - and Friday's test now marks the first time particle tracks have been reconstructed from a man-made event generated by the collider.

"It's amazing to have seen the first LHC tracks," said Themis Bowcock of University of Liverpool, UK, who led the team. "It's quite overwhelming actually," he added.

The purpose of the injection test on August 22 was to make sure protons are magnetically kicked out of the smaller Super Proton Synchrotron (SPS) - the last link in a chain of other CERN accelerators that whip protons up to faster speeds - at the precise moment the LHC is ready to accept them.

For this transfer process to happen smoothly, magnetic pulses in the accelerator chain must be synchronized to within a fraction of a microsecond.

But researchers on the LHCb experiment, which will study B mesons to look for tiny differences in the behaviour of matter and antimatter, spotted an opportunity to put part of their experiment through a test of its own.

On August 22, physicists in the control centre fired a few billion protons from the SPS down a 2.7-kilometre transfer line into a 28-tonne concrete collimator positioned at the entrance to the LHC, some 200 metres upstream from the LHCb detector.

Muons produced in the pileup sailed straight through the block and traveled along the LHC beam pipe to generate electrical hits in successive silicon discs of the Vertex Locator (VELO), an instrument that will track particles produced within a few millimetres of the proton-proton collisions.

Greeted by claps and cheers, the team then used software to display the paths of about half a dozen muons on a laptop screen within minutes of the event.

The first useful physics data is expected to come in October, when the two counter-rotating beams of protons racing through the LHC's 27-kilometre-long tunnels are made to collide, packing sufficient energy into a small enough space to produce fundamental particles from thin air.

ANI