After the early announcement on Friday that CERN had successfully circulated the first protons around the 17 mile-long ring of the Large Hadron Collider (LHC), really early news of the first ever particle collisions inside the LHC has been announced.
According to several sources, these low-energy collisions weren't expected for another two weeks, but LHC scientists and engineers were obviously very confident that they could put the delay to an end and start smashing protons today.
"This is a very exciting moment after so many years of preparation," said Andrew Lankford from the University of California, Irvine, deputy spokesperson for the ATLAS experiment.
The first particle detector to see the colliding protons was the ATLAS detector, which recorded its first collision event at 2:22pm local time on Nov. 23.
On Nov. 20, LHC scientists were able to circulate "beams" of protons, but the billions of particles confined to these beams were unstable and unsuitable for collision purposes. Soon after, counter-rotating beams of protons were circulated, proving that so long as the beams were correctly collimated by the accelerator ring's 1,200 superconducting electromagnets, collisions were soon to become a reality.
And today, after 14 months of delays caused by a catastrophic "quench" in September 2008, the LHC has become the world's most advanced (and now functioning) particle collider.
As discussed in the Symmetry Breaking news release, this collision "happened against the odds." When the LHC is fully operational, colliding beams of protons at high energies, each beam will consist of approximately 3,000 "packets" (or groups) of protons. Inside each of these packets there will be over one hundred billion particles. This might sound like a lot, but the packets will be mostly empty space. If accelerated into one another, co-rotating beams would simply pass straight through one another with minimal chance of collisions.
This is where the skill of CERN engineers and precise nature of the powerful electromagnets come in. Immense control over the relativistic particles are required, so each beam must be as tightly packed as possible on their journey around the accelerator. Only then can the "empty space" be kept to a minimum. This can only be achieved if the LHC is cooled down to nearly absolute zero and the whole system is flawless.
As this low energy collision shows, collimation has been achieved, allowing a number of protons to collide. Now the hunt for the Higgs boson has truly begun!
Image: 3D display of the first 900 GeV candidate collision event showing tracks in the Inner Detector of the ATLAS detector (CERN/LHC/ATLAS). Special thanks to @jonmbutterworth.
Source: Symmetry Breaking
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