LHC creates mini big bangs

The world's largest particle smasher - the Large Hadron Collider at CERN, near Geneva in Switzerland - has seen the highest temperatures ever produced by a science experiment, thanks to a flurry of "mini big bangs".
On 7 November, the LHC started smashing lead ions head-on, instead of the usual proton-proton collisions. This produced what are referred to as mini big bangs: dense fireballs that have temperatures of about 10 trillion °C.
At such temperatures and energies, the nuclei of atoms melt into a mix of their constituent quarks and gluons. The fireball is known as a quark-gluon plasma. The formation of the plasma is a key prediction of the extremely successful theory of quantum chromodynamics (QCD), which tells us that as we go back to earlier and earlier times in the universe's history, the strength of strong interactions falls almost to zero. The discovery of this so-called "asymptotic freedom" is what resulted in a Nobel Prize for David Politzer, Frank Wilczek and David Gross in 2004.
The quark-gluon plasma has been studied in great detail at the Relativistic Heavy Ion Collider (RHIC) at Upton, New York, which smashes gold ions head-on. In February 2010, RHIC researchers reported the creation of plasma that had temperatures of 4 trillion °C.
Now, thanks to a 287 TeV beam, the LHC's lead ions are colliding with energies about 13.5 times greater than what has been achieved at RHIC.The resultant plasma fireballs will allow physicists at CERN using the 10,000-tonne ALICE (A Large Heavy Ion Experiment) detector to study the universe as it was about a millionth of a second after the big bang.
One can only wonder about what surprises are in store. At RHIC, the biggest surprise was that the quark-gluon plasma, instead of being a gas, acts like a perfect liquid.

Beams Are Back

After more than one year of repairs, the LHC is now back on track to create high-energy particle collisions that may yield extraordinary insights into the nature of the physical universe.
"The LHC is a machine unprecedented in size, in complexity, and in the scope of the international collaboration that has built it over the last 15 years," said Dennis Kovar, U.S. Department of Energy Associate Director of Science for High Energy Physics. "I congratulate the scientists and engineers that have worked to get the LHC back up and running, and look forward to the discoveries to come."
American scientists have played an important role in the construction of the LHC. About 150 scientists, engineers and technicians from three DOE national laboratories -- Brookhaven Lab, Fermilab and Berkeley Lab -- built critical accelerator components. They are joined by colleagues from DOE's SLAC National Accelerator Laboratory and the University of Texas at Austin in ongoing LHC accelerator R&D. The work has been supported by the DOE Office of Science.
Circulating beams are a major milestone on the way to the ultimate goal: data from high-energy particle collisions in each of the LHC's four major particle detectors. Over the next few months, scientists will create collisions between two beams of protons. These very first LHC collisions will take place at the relatively low energy of 900 GeV. They will then raise the beam energy, aiming for collisions at the world-record energy of 7 TeV in early 2010. With these high-energy collisions, the hunt for discoveries at the LHC will begin.
"It's great to see beam circulating in the LHC again," said CERN Director General Rolf Heuer. "We've still got some way to go before physics can begin, but with this milestone we're well on the way."
In all, an estimated 10,000 people from 60 countries have helped design and build the LHC accelerator and its four massive particle detectors, including more than 1,700 scientists, engineers, students and technicians from 97 U.S. universities and laboratories in 32 states and Puerto Rico supported by the DOE Office of Science and the National Science Foundation.