The scientist, arrested in France, is suspected of having links to Al Qaeda's North African offshoot, which has carried out a deadly campaign against security forces in recent months, a French official said Friday.
The judicial official said the suspect was one of two brothers arrested Thursday in southeastern French city of Vienne. The official spoke anonymously because the case is ongoing.
The scientist has been assigned to analysis projects at the laboratory since 2003, and was one of more than 7,000 scientists working on the Large Hadron Collider, the world's largest atom smasher, said the European Organization for Nuclear Research, known as CERN.
The physicist had no contact with anything that could be used for terrorism, it said.
"None of our research has potential for military application, and all our results are published openly in the public domain," the organization said.
The LHCb experiment where he worked is the smallest of a series of installations along the 17-mile circular tunnel under the Swiss-French border.