Physics Today: CERN's Large Hadron Collider has finally started colliding two 3.5-TeV circulating beams of protons together to produce 7-TeV collisions and the official start of the LHC research program.
The collisions above (image credit: CERN) occurred at 13:06 Central European Summer Time, according to a live broadcast from CERN, with a couple hundred thousand collisions taken in the first hour.
"It's a great day to be a particle physicist," said CERN director general Rolf Heuer. "A lot of people have waited a long time for this moment, but their patience and dedication is starting to pay dividends."
The collisions almost didn't happen when a power supply tripped and had to be reset says Steve Myers, CERN's director for accelerators and technology. The new safety system that had been installed after technical difficulties in 2008, then shut the system down. New protons were quickly injected back into the ring after the problem was corrected.
Comments from the team
Research teams at the four LHC experiments—ATLAS, ALICE, CMS, and LHCb—say that data delivered from their detectors look good. LHC project leader Lyn Evans cautions however, that it will take some time to run the collider up to maximum efficiency.
"With these record-shattering collision energies, the LHC experiments are propelled into a vast region to explore, and the hunt begins for dark matter, new forces, new dimensions and the Higgs boson," said ATLAS collaboration spokesperson, Fabiola Gianotti. "The fact that the experiments have published papers already on the basis of last year's data bodes very well for this first physics run."
"We've all been impressed with the way the LHC has performed so far," said Guido Tonelli, spokesperson for the CMS experiment, "and it's particularly gratifying to see how well our particle detectors are working while our physics teams worldwide are already analyzing data. We'll address soon some of the major puzzles of modern physics like the origin of mass, the grand unification of forces and the presence of abundant dark matter in the universe. I expect very exciting times in front of us."
"Some of us CMS scientists were in the Fermilab Remote Operations Center most of last night waiting for the first collisions," says Pushpa Bhat, a CMS collaborator. "The collision events were beautiful and we were all like kids
applauding each burst of fireworks!"
"This is the moment we have been waiting and preparing for," said ALICE spokesperson Jürgen Schukraft. "We're very much looking forward to the results from proton collisions, and later this year from lead–ion collisions, to give us new insights into the nature of the strong interaction and the evolution of matter in the early universe."
"LHCb is ready for physics," said LhCb spokesperson Andrei Golutvin. "We have a great research program ahead of us exploring the nature of matter–antimatter asymmetry more profoundly than has ever been done before."
"The LHC team is like a United Nations of physics," says Fred Dylla, executive
director of the American Institute of Physics (which publishes Physics Today), "having brought together thousands of women and men from more than 100 countries around the world over the last few decades."
"Now this assembly has begun the largest scientific experiment in history," Dylla adds. "Never before has so much energy been mustered into so small a space as in these 7-TeV collisions on this first 'world TeV day.'"
A long run
CERN will run the LHC for 18–24 months with the objective of delivering enough data to the experiments to make significant advances across a wide range of physics. As soon as they have calibrated the detectors by "rediscovering" the known standard model particles, the LHC experiments will start the systematic search for the Higgs boson. The latest data from Fermilab suggest however, that the Higgs will not be discovered in this first datarun but will require higher collision energies.
For supersymmetry, ATLAS and CMS will each have enough data to double today's sensitivity to certain new discoveries. Experiments today are sensitive to some supersymmetric particles with masses up to 400 GeV. An inverse femtobarn at the LHC pushes the discovery range up to 800 GeV.
"The LHC has a real chance over the next two years of discovering supersymmetric particles," explained Heuer, "and possibly giving insights into the composition of about a quarter of the universe."
"This LHC run will extend the current [collision energy] reach by a factor of two. LHC experiments will be sensitive to new massive particles indicating the presence of extra dimensions up to masses of 2-TeV; today's reach is around 1-TeV," he adds.
"Over 2000 graduate students are eagerly awaiting data from the LHC experiments," said Heuer. "They're a privileged bunch, set to produce the first theses at the new high-energy frontier."
Shutdown and upgrade
Following this run, the LHC will shutdown for routine maintenance, and to complete the repairs necessitated by the the incident of 19 September 2008 and the consolidation needed to reach the LHC's design energy of 14-TeV.
Traditionally, CERN has operated its accelerators on an annual cycle, running for seven to eight months with a four- to five-month shutdown each year but because the cryogenic machine operates at very low temperature, the LHC takes about a month to come up to room temperature and another month to cool down. A four-month shutdown as part of an annual cycle no longer makes sense for such a machine, so CERN has decided to move to a longer cycle with longer periods of operation accompanied by longer shutdown periods when needed.
"Two years of continuous running is a tall order both for the LHC operators and the experiments, but it will be well worth the effort," said Heuer. "By starting with a long run and concentrating preparations for 14-TeV collisions into a single shutdown, we're increasing the overall running time over the next three years, making up for lost time and giving the experiments the chance to make their mark."
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Related links
Large Hadron Collider finally smashing properly New York Times
World's largest atom smasher breaks record NPR
Large Hadron Collider smashes protons, record Los Angeles Times
Eureka! Large Hadron Collider fires up, smashes protons Christian Science Monitor
Geneva atom smasher sets collision record USA Today
Large Hadron Collider breaks high-energy records The Guardian
Large Hadron Collider achieves success with high energy particle collisions The Daily Telegraph
Record LHC collisions mark new era for physics New Scientist
I have often wondered if the LHC will come up with evidence of aditional quarks and/or charged leptons.
It is a sort of mantra of Standard Model theorists and main-stream cosmologists that there are likely no additional; quarks, heavy electrons, or neutrinos, or that there can exist at most one additional neutrino, the sterile neutrino.
However, consider all of the periodic table elements that were discovered over the previous 2 centuries.
Nature enjoys producing 6 quarks, along with the 6 antiquarks, which is already a large number. Even the roughly thousand plus number of known isotopes, except H1 are produced from only three particles, not counting the internal quarks that comprise the nucleons, and so perhaps the fact that there are 6 known quarks, a number that is equal to 2 x 3, might suggest a deeper level of composition, and additional extremely heavy quarks. If there are additional quarks, then just perhaps additional gluons exist, whether or not some or all of these additional gluons would exist as a superposition of known or yet to be discovered or contrived gluons.
Perhaps a similar argument can be made regarding the charged leptons.
Perhaps any additional complexity within the strong nuclear force and/or weak force would offer a greater number of qualitiatively differing thermodynamic degrees of freedom on which to develop novel interstellar space craft propulsion systems based on new physics.