Nov. 24, 2009
Researchers celebrate restart, first collisions at world's largest atom smasher
Two University of Iowa research groups are celebrating the recent restart of the nearly $10 billion scientific tool that will enable them to continue searching for the basic building blocks of all matter.
The scientific tool is the world's largest atom smasher -- the Large Hadron Collider (LHC) accelerator at the European Organization for Nuclear Research (CERN) in Geneva, Switzerland. The LHC's first collisions of proton beams occurred Nov. 23, following an earlier restart that involved getting particle beams re-circulating after more than a year of repairs.
In September 2008, when scientists switched on the LHC for the first time, they anticipated that its powerful magnets would accelerate two beams of protons around the 17-mile ring in opposite directions with each beam having a potential energy of nearly seven trillion electron volts (TeV). That is about seven times the power of the next-most-powerful machine, located at Fermilab near Chicago.
Instead, nine days after the injection of the first proton beams, an electrical failure caused a large helium leak, and the LHC was forced to shut down before it was able to begin colliding particles. One year later, however, the LHC has been repaired and proton beam collisions are taking place.
"These first proton collisions are not at high energies (900 billion electron volts or 900 GeV total energy), but they are a start. If all goes well, higher energy proton-proton beam collisions will take place around Christmas or after New Year's Eve," said Yasar Onel, professor of physics in the UI College of Liberal Arts and Sciences. "Physicists will obtain a large amount of data from these early collisions, but will spend the first few months calibrating the electronics of the detector so that complex analyses can take place in 2010."
The Onel team's contribution to the project is a particle detector called the "subdetector HF-Forward Calorimetry device." Designed and developed at UI machine shops, it became the first detector to go underground in the Compact Muon Solenoid (CMS) collision hall in November 2007.
The UI forward calorimeter will measure the energy of particles moving in a forward direction after a proton collision has taken place at the center of a total energy mass of 14 TeV -- enough energy to replicate, in miniature, conditions present shortly after the creation of the universe. The calorimeter's quartz fibers give off light when struck by particles released by the proton collisions.
The UI CMS team includes Onel, Associate Professors Jane Nachtman and Charles Newsom, Emeritus Professors Ed Norbeck and Ed McCliment, Adjunct Assistant Professor Ugur Akgun, Project Scientist J.P. Merlo, four post-doctoral fellows seven graduate students and two engineers. About one-third of the 1,500 CMS physicists are U.S. scientists who work through the U.S. Department of Energy's Fermi National Accelerator Laboratory in Batavia, Ill.
James Wetzel, a graduate student of Nachtman, noted the delay was unfortunate but has allowed a lot more "hands-on" time with the detector, thereby greatly improving the likelihood of discovering new physics at the LHC's energy frontier.
Usha Mallik, professor of physics, leads another team of UI researchers. Mallik's research team is working on the seven-story-tall ATLAS (A Toroidal LHC ApparatuS) particle detector in the underground collision hall of the LHC. Like CMS, the ATLAS experiment is designed to observe phenomena that involve highly massive particles, which were not seen using older, lower-energy accelerators.
Mallik and her group of UI scientists include: Prafulla Behera, assistant research scientist, Maaike Limper, Christoph Pahl and Remi Zaidan working as postdoctoral fellows. A total of 38 U.S. universities are participating in the ATLAS experiment, a collaboration consisting of 2,100 people from more than 30 countries.
Mallik and her group are leading several areas in what will be the first physics results from ATLAS, called Minimum Bias Analysis. This analysis will help scientists understand the characteristics of the detector with real data by comparing it with data from the simulated detector model that has been used up until now. It will also measure what the real event rates from the collisions are going to be as opposed to predictions from several different models.
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 U.S. Department of Energy Office of Science and the National Science Foundation.
STORY SOURCE: University of Iowa News Services, 300 Plaza Centre One, Iowa City, Iowa 52242-2500
MEDIA CONTACT: Gary Galluzzo, writer, 319-384-0009, firstname.lastname@example.org