LHCb magnet and iron yoke.
Image Copyright CERN
|
Five undergraduate students at the University of Cambridge were among the first to use grid computing tools to analyze data for the LHCb particle physics experiment. In research projects completed as part of the MSci degree, the students used simulated data to study the decays of B mesons, paving the way for physicists to solve the mystery of missing antimatter.
"So far the LHCb grid system has mainly been used for the production of simulated data," says Cristina Lazzeroni from the University of Cambridge, one of the students' supervisors on the project. "If they were to use the local computer batch queues for the analysis the students would have been competing with one another for scarce resources. To avoid this, it was essential to use the grid."
When the Large Hadron Collider, currently being built in Geneva, Switzerland, begins operating in 2008, scientists from the LHCb experiment will study the decays of the B mesons produced when two very-high-energy protons collide. By examining one set of decays physicists can study the origin of CP violation, in an attempt to explain why the universe is made mostly of matter and very little antimatter. B decays can also be used to search for evidence of new physics, such as exotic particles like squarks and gluinos.
Kelly, Willans, Lum and others at the Second LHCb-UK Software Course.
Image Courtesy GridPP
|
"One of the students studied the decay of the B to three other particles: a K* and two muons," explains Lazzeroni. "That way in which the B decays is very sensitive to the presence of new physics. Essentially you would examine how the muons are produced, the direction that the K* and the two muons travel with respect to each other."
The students' projects were to devise methods to separate the very few decays that they were interested in—K* and two muons, for example—from the enormous amount of background data generated each time two protons collide in the LHCb detector. Such studies required analyzing the background data thoroughly, which meant processing 700-gigabyte simulation data samples many times over.
The undergraduates' first introduction to grid computing came during a LHCb-UK Software Training session held at Cambridge in January. One half day was devoted to grid computing, and at the end of the session the students were successfully submitting jobs to the grid using a tool called Ganga that was developed by LHCb grid researchers to simplify grid submission. By the end of May, they had progressed to submitting large analysis jobs to sites around the world, in the end processing more than five terabytes of data, equal to more than 70 million simulated B decays.
All five students—Marta Dobrowolski, Stuart Kelly, Brian Lum, Ruth Dixon del Tufo and Adam Willans—graduated in July. The work of at least three of the students will be published by the LHCb collaboration as an LHCb Note and will be used by physicists in the future to refine their analysis processes.
Learn more at the GridPP Web site.
—Katie Yurkewicz
e-mail this article
|
