Tufts researchers contribute to particle accelerator experiment

A consortium of Boston-area researchers hopes to fill in a missing piece of a fundamental theory of physics within the next couple months, when groundbreaking tests are carried out at the world’s largest and most powerful particle accelerator.

The group of researchers will analyze data from an experiment to take place in the Large Hadron Collider (LHC), a 17-mile-long particle accelerator located under the French-Swiss border. Built by the European Organization for Nuclear Research (CERN) near Geneva, the LHC has been plagued by setbacks since researchers first used it briefly in Sept. 2008, but it is set to fully start back up next month.

Tufts students and faculty members, partnering with physicists from the Massachusetts Institute of Technology and Boston, Harvard and Brandeis Universities, hope “to find out more things about fundamental particles,” according to Austin Napier, a Tufts professor of physics and astronomy who is participating in the project.

The consortium’s work centers on ATLAS (A Toroidal LHC Apparatus) detector, one of six experiments in the LHC. Researchers in the Tufts delegation will take advantage of data gleaned from ATLAS’ tests to study specific aspects of fundamental particles.

An electrical failure led to a coolant leak within days of the LHC’s opening last year, forcing it to shut down and placing experiments on hold until now.

The LHC is set to resume normal operations next month. Last week, a preliminary test of the collider’s equipment beamed particles most of the way through the accelerator.

In LHC experiments, two beams of subatomic particles, or hadrons, are smashed together at high energy levels.

Over the past few years, the Boston group — called the Boston Muon Consortium — has helped build parts of the muon detection system for the LHC, according to Napier. Muons are negatively charged subatomic particles.

The physical construction of the system’s parts took place at Harvard, and “Tufts and Brandeis played a big role in its design,” Napier said.

Krzysztof Sliwa, a professor of physics and astronomy, heads up the Tufts team.

Napier and Simona Rolli, a team member and research associate in the departments of physics and astronomy, are most interested in using data from the experiment to verify the existence of the Higgs boson, an elementary particle that has been predicted to exist but has so far remained undetected.

The Boston researchers’ work could change this. Data confirming the existence of the Higgs boson would complete the Standard Model of particle physics, a theory that attempts to explain the existence and interactions of three or four fundamental visible particles.

Other members of the consortium are more concerned with top-quark physics and muons.

Napier said he is “not optimistic about finding the Higgs [particle] for at least a year.” Still, he said, “there’s always room for surprises.”

Napier and Rolli have written much of ATLAS’ software and the software used to analyze data from the experiment. Napier hopes to set up a live display in Anderson Hall of the data collected from the collisions.

ATLAS experiments began last spring but were pushed back because some of the magnets that line the collider developed spots that were more resistive and would heat up during particle accelerations, eventually causing the magnets to push apart, according to Napier.

The system was repaired over the summer. “The energy [used in the collisions] will be lower than originally hoped” this time due to safety precautions, Napier said.

“People are optimistic that things will work,” he added.

The Tufts team also includes two graduate students, Samuel Hamilton and Jeffrey Wetter. Hamilton has spent the last two summers at CERN working on the project.

Junior Matt Rosenfield, meanwhile, is helping Napier put together data displays.

In the past, Tufts faculty members have called on students to help build and design the components of ATLAS, but with the project just weeks from beginning, this kind of hands-on work will only occur if the group decides to upgrade the experiment’s technology in the future.

Rolli believes the spirit of international cooperation is very much alive at CERN, which involves thousands of scientists from around the world.

As part of the program, “you feel very much the sense of being in a team,” he said.