Indiana University physicists are working on the upgrade of the world’s largest and most powerful particle accelerator, the Large Hadron Collider, in Geneva, Switzerland.
Hal Evans, IU professor of physics, is the deputy project manager overseeing the U.S. $300 million share of the upgrade.
The Collider is operated by CERN, the European Center for Nuclear Physics. It propels protons or ions to near the speed of light, so that two high energy particle beams can collide. It is used to advance knowledge of the foundation of physics.
The upgrade will make the accelerator able to produce more intense proton beams, Evans said. For its ATLAS experiment, and its sister experiment CMS, changes will be made to its detectors and to the electronics that read those detectors, to cope with more intense proton beams, Evans said.
ATLAS is one of two general purpose detectors at the Large Hadron Collider. IU is among 245 institutions from more than 40 countries which work on the ATLAS experiment. It involves around 6,000 physicists, engineers, technicians and students. ATLAS detects what comes out of proton-proton collisions produced by the Large Hadron Collider, he said.
“It has approximately a little bit more than 10 million individual channels of when it's read out, and a large number of different detector technologies that are sensitive to different aspects of the particles that are produced when protons collide in the center of the detector,” Evans said.
This is the largest upgrade to the experiment; two prior smaller upgrades were made, he said. The new detector will have more than 10 billion readout channels.
“All of those have to be connected,” he said. “They all have to be tested, and then we can start. Then we can start running. We can start taking data.”
The upgrade to the Large Hadron Collider is a step toward extending the Standard Model theory to explain aspects such as dark matter and dark energy. Dark matter makes up about 25 percent of the universe and dark energy makes up about 65 percent, Evans said.
The Standard Model theory explains three out of the four fundamental building blocks of force: electromagnetism, weak force and strong force. Gravity is not described by the theory.
This current upgrade aims to produce more data, Evans said. “The energy of the beams will go up by a small amount but will produce almost a factor of 10 more data than we have now, so that means we can look for things that are a factor of 10 rarer and even below that.”
For this upgrade, the accelerator shut down in July and will remain so for about three and a half years. If all goes according to plan, the machine will start taking data again in summer 2030, which will be the start of Run Four. The plan for that is called the High Luminosity Large Hadron Collider period, which will last for about a decade and consist of multiple data runs, Evans said.
“So, it took a long time in order to accumulate enough data to see to see that Higgs boson, so that's what we're looking for in in Run Four, Run Five, the HL-LHC era, is gradually accumulating enough data to see something really new,” he said.
Higgs boson, the last of the particles predicted in the Standard Model theory, was discovered in Run Two.
The accelerator runs during the spring, summer and fall seasons. It shuts down during winter for maintenance and repairs. Every few years, a longer shutdown occurs for significant upgrades like this one, Evans said.
