The LHC is inside a 27 km tunnel 100 meters underground as indicated by
the circle shown. The Geneva airport runway in Switzerland is on the right.
The end view of the A Toroidal LHC ApparatuS (ATLAS) detector before
closing. There are 4 detectors in LHC. This ATLAS Collaboration has about
3,000 physicists working together. They came from 180 universities and
institutes from 40 countries. Hong Kong joined ATLAS in 2014.
By Tao Liu (Assistant Professor, Department of Physics, HKUST) and
Yanjun Tu (Assistant Professor, Department of Physics, HKU)
LHC is Back,
withBig Data!
After two years of maintenance and upgrade, the Large
Hadron Collider (LHC) at the European Organization for
Nuclear Research (CERN), the most powerful particle
accelerator in the world, is back in operation on 5 April
2015, as reported in the news media. This brings the LHC
to its Run II era. During Run I (2009-2012), the Higgs Boson
(the God particle), a key element to understand the mass
generation of all basic particles (such as the electron) in the
universe, was discovered. This discovery was named
2012’s “Breakthrough of the Year” by Science magazine.
The upgrade of the LHC has been very successful so far.
Operating at an unprecedented energy
–
almost double
that of Run I
–
at 13 trillion electron volts (TeV) for a single
proton-proton collision, the LHC experiments will soon be
exploring uncharted territories probing the fundamental
laws in nature.
At the LHC, for every 50 or 25 nano-seconds, two beams
of proton-proton bunches cross each other and produce
thousands of particles. The passage of those particles is
recorded by the detector electronic systems. The
electronic signals are processed by sophisticated
computers. During Run I, there were about 15,000 trillion
bytes (15 petabytes) data collected (a small fraction of the
total data produced) - more than the data of all the videos
uploaded to YouTube annually. Eventually 400 petabytes
data per year are expected from the LHC future runs
before Year 2030. Processing such big data sets is
extremely challenging in many aspects including capturing,
storing, transferring, visualizing and analyzing them in a
limited time by collaborators that are spread world-wide.
Knowledge Corner
May 2015
6
