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Physicists have been Programming Trigger Software that Must Quickly and Accurately Decide Important Data
:: 10 April, 2008
Thousands of scientific visitors regularly descend upon the European Organization for Nuclear Research (CERN). Home of the Large Hadron Collider (LHC), the newest and largest particle accelerator, makes CERN a frequent destination for visiting collaborators, many of whom are from SLAC.
"I end up spending more time at CERN than I do at SLAC," physicist Charlie Young said. "I wouldn't do all this traveling, if it weren't for the physics."
One particular center of SLAC's involvement at the LHC is the A Toroidal LHC ApparatuS (ATLAS) experiment, one of six detectors situated at collision interaction points. Nearly 2,000 ATLAS collaborators worldwide are busy finalizing the detector, which will scour data from the uncharted high-energy frontier.
In the LHC, billions of protons will collide 40 million times a second, but only about 200 of these events will be recorded. Clearly, scientists want to probe the most interesting interactions for the possibility of "new" physics. To separate the known from the unknown, SLAC physicists, along with others, have been programming trigger software that must quickly and accurately decide which data to keep or ignore.
SLAC scientists have also contributed to ATLAS's pixel detector. Deeply embedded within the core of the structure, the detector is uniquely suited for not only tracking the trajectories of particles, but pinpointing the origins of interactions.
As a whole, ATLAS works remarkably well, especially considering the complexity of its components and massive size. However, ATLAS collaborators are still working on numerous facets of the project. Other areas that SLAC is aiding the overall effort include detailed data simulations, which will include real data and data based on the best current approximations.
Note for Large Hadron Collider
The Large Hadron Collider (LHC) is a particle accelerator located at CERN, near Geneva, Switzerland. It lies in a tunnel under France and Switzerland.
It is currently in the final stages of construction, and commissioning, with some sections already being cooled down to its final operating temperature of ~2K (−271°C). The first beams are due for injection mid June 2008 with the first collisions planned to take place 2 months later. The LHC will become the world's largest and highest-energy particle accelerator. The LHC is being funded and built in collaboration with over two thousand physicists from thirty-four countries as well as hundreds of universities and laboratories.
When activated, it is theorized that the collider will produce the elusive Higgs boson, the observation of which could confirm the predictions and "missing links" in the Standard Model of physics and could explain how other elementary particles acquire properties such as mass. The verification of the existence of the Higgs boson would be a significant step in the search for a Grand Unified Theory, which seeks to unify the three fundamental forces: electromagnetism, the strong nuclear force and the weak nuclear force. The Higgs boson may also help to explain why gravitation is so weak compared to the other three forces. In addition to the Higgs boson, other theorized novel particles that might be produced, and for which searches are planned, include strangelets, micro black holes, magnetic monopoles and supersymmetric particles.
The collider is contained in a circular tunnel with a circumference of 27 kilometres (17 mi) at a depth ranging from 50 to 175 metres underground. The tunnel, constructed between 1983 and 1988, was formerly used to house the LEP, an electron-positron collider.
The 3.8 metre diameter, concrete-lined tunnel crosses the border between Switzerland and France at four points, although the majority of its length is inside France. The collider itself is located underground, with many surface buildings holding ancillary equipment such as compressors, ventilation equipment, control electronics and refrigeration plants.
The collider tunnel contains two pipes enclosed within superconducting magnets cooled by liquid helium, each pipe containing a proton beam. The two beams travel in opposite directions around the ring. Additional magnets are used to direct the beams to four intersection points where interactions between them will take place. In total, over 1600 superconducting magnets are installed, with most weighing over 27 tonnes.
The LHC physics program is mainly based on proton-proton collisions. However, shorter running periods, typically one month per year, with heavy-ion collisions are included in the programme. While lighter ions are considered as well, the baseline scheme deals with lead (Pb) ions. This will allow an advancement in the experimental programme currently in progress at the Relativistic Heavy Ion Collider (RHIC).
The construction of LHC was originally approved in 1995 with a budget of 2.6 billion Swiss francs, with another 210 million francs (140 M€) towards the cost of the experiments. However, cost over-runs, estimated in a major review in 2001 at around 480 million francs (300 M€) in the accelerator, and 50 million francs (30 M€) for the experiments, along with a reduction in CERN's budget pushed the completion date out from 2005 to April 2007. 180 million francs (120 M€) of the cost increase has been the superconducting magnets. There were also engineering difficulties encountered while building the underground cavern for the Compact Muon Solenoid, due to, in part, the allegedly "faulty" parts lent to CERN by fellow laboratory and home to the world's largest particle accelerator, (until CERN finishes the Large Hadron Collider) Argonne National Laboratory, or FermiLab, located in Batavia, Illinois, outside of Chicago. The total cost of the project is anticipated to be between $5 and $10 billion (US Dollars).
About European Organization for Nuclear Research
The European Organization for Nuclear Research is the world's largest particle physics laboratory, situated in the northwest suburbs of Geneva on the border between France and Switzerland. The convention establishing CERN was signed on 29 September 1954. From the original 12 signatories of the CERN convention, membership has grown to the present 20 member states. Its main function is to provide the particle accelerators and other infrastructure needed for high-energy physics research. Numerous experiments have been constructed at CERN by international collaborations to make use of them.
The main site at Meyrin also has a large computer centre containing very powerful data processing facilities primarily for experimental data analysis, and because of the need to make them available to researchers elsewhere, has historically been (and continues to be) a major wide area networking hub.
CERN currently has approximately 2600 full-time employees. Some 7931 scientists and engineers (representing 500 universities and 80 nationalities), about half of the world's particle physics community, work on experiments conducted at CERN.
The acronym CERN originally stood, in French, for Conseil Européen pour la Recherche Nucléaire (European Council for Nuclear Research), which was a provisional council for setting up the laboratory, established by 11 European governments in 1952. The acronym was retained for the new laboratory after the provisional council was dissolved, even though the name changed to the current Organisation Européenne pour la Recherche Nucléaire (European Organization for Nuclear Research) in 1954. According to Lew Kowarski, a former director of CERN, when the name was changed, the acronym could have become the awkward OERN, and Heisenberg said "But the acronym can still be CERN even if the name is [not]".
In figure, The pixel detector installed at the core of ATLAS will help track particles in the massive detector
Tags: European Organization for Nuclear Research (CERN) , Large Hadron Collider (LHC) , particle accelerator , SLAC , Charlie Young , Toroidal LHC ApparatuS (ATLAS) experiment ,
