UW News

March 5, 2019

FASER detector at the Large Hadron Collider to seek clues about hidden matter in the universe

An aerial view of a particle physics experiment in Europe.

A 2008 aerial image of the LHC site, which straddles the border between France and Switzerland, with major LHC and CERN installations outlined and labeled.CERN

The research board of CERN, the European Organization for Nuclear Research, on March 5 approved a new experiment at the Large Hadron Collider in Geneva, the world’s largest particle accelerator, to search for evidence of fundamental dark matter particles. The Forward Search Experiment — or FASER — seeks to answer one of the outstanding questions in particle physics: What is dark matter made of?

“There is strong evidence that most of the matter in the universe — about 85 percent — is dark matter, and that dark matter is made up of an unknown class of fundamental particles,” said Shih-Chieh Hsu, an associate professor of physics at the University of Washington and member of the FASER team. “The identity of dark matter particles is a major mystery in particle physics, and one that we think FASER could help solve by identifying a class of particles associated with dark matter.”

FASER is a partnership of 16 institutions around the globe, including the UW, and co-led by scientists at the University of California, Irvine and CERN, which operates the Large Hadron Collider, or LHC. The five-year FASER project is funded by grants of $1 million each from the Heising-Simons Foundation in California and the Simons Foundation in New York, with additional support from CERN.

FASER is trying to find indirect evidence for the light, weakly interacting particles that may interact with dark matter. So far, these particles have eluded scientists. But the FASER team will try to detect traces of these particles as they decay from the LHC’s proton beams.

“Seven years ago, scientists discovered the Higgs boson at the Large Hadron Collider, completing one chapter in our search for the fundamental building blocks of the universe, but now we are looking for new particles,” said Jonathan Feng, FASER co-spokesperson and professor of physics and astronomy at UC Irvine. “The dark matter problem shows that we don’t know what most of the universe is made of, so we’re sure new particles are out there.”

The FASER instrument is designed to be compact, measuring about 1 meter in diameter and 5 meters long. It will be placed at a specific point along the 16-mile loop of the LHC, about 480 meters, or 1,574 feet, away from the hulking, six-story instrument used by the ATLAS Collaboration to discover the Higgs boson.

A computer image of a device that will detect particles in the Large Hadron Collider.

This computer drawing shows the FASER instrument in a tunnel at CERN’s Large Hadron Collider in Geneva, Switzerland. The detector will be precisely aligned with the collision axis in the ATLAS instrument 480 meters away. FASER will track and measure the decay of particles produced.FASER/CERN

As proton beams pass through the interaction point at the ATLAS instrument, some theories indicate that they may decay to a candidate particle that interacts with dark matter, a dark photon, which in turn could decay into a pair of particles — an electron and a positron — as it passes through concrete in the LHC tunnel and then into the FASER instrument. The instrument will be able to measure the progress of particle decay, and will collect data when ATLAS is operating.

“The high number of particles at the LHC gives us this irresistible chance to try to detect new lightweight particles — and even trace them as they travel hundreds of meters from their source to the detector,” said Hsu.

At the UW, Hsu’s group studies simulations of detection events by the FASER instrument, working out the instrument parameters and data-analysis tools needed to accurately trace any detected particles back to their sources. These tools will help separate real signals of dark matter-associated particles from background events.

“One of the advantages of our design is that we’ve been able to borrow many of the components of FASER — silicon detectors, calorimeters and electronics — from the ATLAS and LHCb collaborations,” said Jamie Boyd, CERN research scientist and co-spokesperson for FASER. “That’s allowing us to assemble an instrument that costs hundreds of times less than the largest experiments at the LHC.”

The detector’s support platform, which will hold intricate magnets and detectors in place, will be designed and manufactured by a UW team led by laboratory engineer Bill Kuykendall in the Department of Mechanical Engineering, with input from UW physics professor Henry Lubatti.

The FASER detector, which will be one of only eight research instruments at the LHC, is being built and installed during the collider’s current hiatus and will collect data from 2021 to 2023. The LHC will be shut down again from 2024 to 2026. During that time, the team hopes to install the larger FASER 2 detector, which will be capable of unveiling an even wider array of mysterious, hidden particles.

The FASER team will consist of 30 to 40 members, a relatively small number compared to other groups conducting research at the LHC. In addition to CERN, UC Irvine and the UW, other institutions participating in the FASER endeavor are the University of Oregon, Rutgers University, the University of Geneva in Switzerland, the University of Bern in Switzerland, Italy’s National Institute for Nuclear Physics Genoa Section, China’s Tsinghua University, Technion – Israel Institute of Technology, Israel’s Weizmann Institute of Science, the Johannes Gutenberg University of Mainz in Germany, Kyushu University in Japan, Nagoya University in Japan, the “KEK” High Energy Accelerator Research Organization in Japan and the University of Sheffield in the U.K.


For more information, contact Hsu at schsu@uw.edu or 206-543-2760.

Adapted from a release by the University of California, Irvine.