U.S. CMS collaborators receive approval for massive detector upgrade

The U.S. Department of Energy has formally approved the start of full production for the $200 million DOE-funded contributions to the upgrade of the CMS experiment at CERN. Together with contributions from other international partners, the upgrade will significantly improve the capabilities of the CMS detector and enable scientists to explore uncharted territory on the particle physics landscape.

“We want to understand what nature is telling us,” said Patty McBride, the CMS spokesperson and a distinguished scientist at DOE’s Fermi National Accelerator Laboratory. “These upgrades will allow us to extract more information from our detector and unlock more about the world and universe.”

CMS is an international collaboration of scientists who study the fundamental properties of matter using the CMS detector at CERN, an international physics laboratory on the Franco-Swiss border. More than 1,800 researchers from U.S. institutions work on the experiment.

Physicists use the CMS detector to collect data from high-energy particle collisions produced by the Large Hadron Collider, the world’s biggest particle accelerator. At the end of the decade, the scientific reach of the LHC will become even more impressive thanks to the high-luminosity upgrade to the machine, which will begin in 2026. The recently released recommendations by the U.S. Particle Physics Project Prioritization Panel, known as the 2023 P5 report, lists the completion of the HL-LHC as a top priority for the U.S. particle physics community.

The upgrade will increase the collision rate by a factor of five, giving scientists a massive dataset to look for new particles and study rare subatomic processes. To keep up with the more intense particle beams, the CMS experiment needs a massive overhaul.

“We need new functionalities to cope with the harsh HL-LHC environment,” said Fermilab scientist Steve Nahn, the project manager for the U.S.-funded CMS upgrade. The project also receives funding from the U.S. National Science Foundation and is part of the international CMS upgrade plan.

Between 2029 and 2042, CMS scientists plan to collect 10 times more data than recorded since the startup of the LHC in 2010. Among many scientific goals, the additional data will enable scientists to develop a deeper understanding of the Higgs boson and how the Higgs field influenced the development and acted as dispersant of matter in the early universe.

“It’s not just looking at what’s unexpected; it’s also about having a deeper understanding of the particles we already know about, especially the Higgs,” McBride said.

The rapid increase in data poses many challenges. The experiment will go from seeing about 60 proton-proton collisions every time the LHC beams cross to around 200. This jump in collision rate means that scientists not only need more bandwidth on their electronics, but new components that will help them get the most out of this surge in data. For example, a new timing detector will tag particles emerging from the collisions with an accuracy of around 30 picoseconds, giving scientists the ability to better determine the trajectory of the particles and gain a better understanding of how the particles interacted with each other.

“We’re not just replacing old pieces; we are pushing the envelope,” Nahn said. “The HL-LHC is going to be a proving ground for new detector technology.”

The U.S.-funded work will be carried out by scientists, engineers and technicians from Fermilab and 45 universities located in 23 states. Much of the work will be done by students, who make up a sizable fraction of the experiment.

“This is a huge opportunity for students,” said Robin Erbacher, a professor at the University of California, Davis, and the chair of the U.S. CMS collaboration board. “We don’t build detectors every day.”

 

The worldwide CMS collaboration—which comprises 6,000 scientists from 57 countries—has been planning detector upgrades since the early 2000s. In 2016, the U.S.-funded CMS institutions, which make up about one-third of the collaboration, started the approval process with the US funding agencies for their planned contributions.

“This has been in the works for a long time,” Erbacher said.

During the approval process for the upgrade project, experts reviewed the physics goals, technical design reports, construction schedules and cost for the proposed detector components. The DOE approval, known as Critical Decision 3 and announced on January 11, allows the U.S.-funded CMS collaborators to move into full production on the proposed upgrades.

U.S. CMS collaborators will complete and ship their contributions to CERN between 2026 and 2027. The start-up of the high-luminosity LHC is foreseen for 2029.

Fermi National Accelerator Laboratory is supported by the Office of Science of the U.S. Department of Energy. The Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov.

Excavation workers have finished carving out the future home of the gigantic particle detectors for the international Deep Underground Neutrino Experiment. Located a mile below the surface, the three colossal caverns are at the core of a new research facility that spans an underground area about the size of eight soccer fields.

Hosted by the U.S. Department of Energy’s Fermi National Accelerator Laboratory, DUNE scientists will study the behavior of mysterious particles known as neutrinos to solve some of the biggest questions about our universe. Why is our universe composed of matter? How does an exploding star create a black hole? Are neutrinos connected to dark matter or other undiscovered particles?

The caverns provide space for four large neutrino detectors—each one about the size of a seven-story building (see 2-minute animation). The detectors will be filled with liquid argon and record the rare interaction of neutrinos with the transparent liquid.

Trillions of neutrinos travel through our bodies each second without us even knowing it. With DUNE, scientists will look for neutrinos from exploding stars and examine the behavior of a beam of neutrinos produced at Fermilab, located near Chicago, about 800 miles east of the underground caverns. The beam, produced by the world’s most intense neutrino source, will travel straight through earth and rock from Fermilab to the DUNE detectors in South Dakota. No tunnel is necessary for the neutrinos’ path.

“The completion of the excavation of these enormous caverns is a significant achievement for this project,” said U.S. Project Director Chris Mossey. “Completing this step prepares the project for installation of the detectors starting later this year and brings us a step closer towards fulfilling the vision of making this world-class underground facility a reality.”

Engineering, construction and excavation teams have been working 4,850 feet below the surface since 2021 at the Sanford Underground Research Facility, home of the South Dakota portion of DUNE.  Construction crews dismantled heavy mining equipment and, piece by piece, transported it underground using an existing shaft. Underground, workers reassembled the equipment, and workers spent almost two years blasting and removing rock. Close to 800,000 tons of rock were excavated and transported from underground into an expansive former mining area above ground known as the Open Cut.

Workers will soon begin to outfit the caverns with the systems needed for the installation of the DUNE detectors and the daily operations of the research facility. Later this year, the project team plans to begin the installation of the insulated steel structure that will hold the first neutrino detector. The goal is to have the first detector operational before the end of 2028.

“The completion of the three large caverns and all of the interconnecting drifts marks the end of a really big dig. The excavation contractor maintained an exemplary safety record working over a million hours without a lost-time accident. That’s a major achievement in this heavy construction industry,” said Fermilab’s Michael Gemelli, who managed the excavation of the caverns by Thyssen Mining. “The success of this phase of the project can be attributed to the safe, dedicated work of the excavation workers, the multi-disciplined backgrounds of the project engineers and support personnel. What a remarkable achievement and milestone for this international project.”

DUNE scientists are eager to start the installation of the particle detectors. The DUNE collaboration, which includes more than 1,400 scientists and engineers from over 200 institutions in 36 countries, has successfully tested the technology and assembly process for the first detector. Mass production of its components has begun. Testing of the technologies underlying both detectors is underway using particle beams at the European laboratory CERN.

Fermilab is America’s premier national laboratory for particle physics and accelerator research. A U.S. Department of Energy Office of Science laboratory, Fermilab is located near Chicago, Illinois, and operated under contract by the Fermi Research Alliance LLC. Visit Fermilab’s website at www.fnal.gov and follow us on Twitter at @Fermilab.

The DOE Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov.

Using nonstick cookware to fry your bacon and eggs can make your life easier at that moment, but scientists believe there may be long-term consequences because the chemicals used to make it nonstick are so difficult to destroy. Perfluoroalkyl and polyfluoroalkyl substances — commonly known as PFAS and often called forever chemicals — are everywhere. PFAS, a suite of thousands of chemicals that have been around at least since the 1950s, are used for a wide variety of things, from the stain protectant on some of your clothing and linens to the food wrappers on your burgers.

The problem is that natural processes are ineffective at breaking PFAS down, so they accumulate in the environment and body, much like Styrofoam does in a landfill. Experts in science and industry are seeking ways to prevent PFAS contamination from occurring in the future, but they also aim to reduce what already exists in the world today.

It turns out that high-energy electron beams are excellent candidates for destroying PFAS in the environment. Researchers at the U.S. Department of Energy’s Fermi National Accelerator Laboratory, in collaboration with 3M, have successfully demonstrated that an electron beam can destroy the two most common types of PFAS in water — PFOA and PFOS.

“The electron beam is a promising technology to break down PFAS in large volumes of water that contain high concentrations of PFAS,” said Fermilab principal investigator Charlie Cooper.

The Fermilab team, which includes scientist Slavica Grdanovska, engineering physicist Yichen Ji and Cooper, used an electron beam accelerator at the laboratory for their testing. Used for proof-of-concept testing, the Accelerator Application Development and Demonstration accelerator, or A2D2, at the Illinois Accelerator Research Center on Fermilab’s campus is also available to industry, universities and other federal laboratories as a research tool.

“The fact that we were working with 3M, a world expert in PFAS, was really the first time that you had the experts on ionizing radiation, electron beam accelerators and PFAS working on the same project,” said Cooper.

Electron beams to the rescue

Conventional water treatment methods, such as reverse osmosis, granular activated carbon or ion exchange resin, do not destroy PFAS; they simply concentrate PFAS in a form which subsequently requires treatment or disposal. In some cases, conventional water treatment techniques can even make the environmental contamination worse.

In contrast, the electron beam actively destroys the forever chemicals and does so quickly, enabling a larger volume of water to be treated in the same amount of time as some other methods. PFAS molecules are difficult to break down because they contain a carbon-fluorine bond, which is very strong and the reason PFAS are commonly used in the chemical manufacturing industry. But the strength of that C-F bond is also the reason they don’t break down in nature. The electron beam, however, is very effective at breaking that C-F bond.

Electron beams could be used in pump-and-treat methods, a common groundwater treatment approach, or in a manufacturing facility, directly treating waste streams before they leave the facility.

Demonstrating its effectiveness

The Fermilab team used PFAS-contaminated water samples provided by 3M that were sealed in gastight containers the size of a whiteboard marker. Each of the containers was made of borosilicate glass, which wouldn’t be significantly affected by exposure to electron beams, and an aluminum seal was crimped onto the glass with a piece of PFAS-free rubber between the aluminum and the glass. Great care was taken to ensure there were no PFAS in any of the materials used to house the samples. Fermilab irradiated these samples with the electron beam and shipped them back to 3M.

3M sampled both the headspace — the air at the top of the container — and the liquid to verify that the PFAS of concern had been destroyed without releasing hazardous products to the air.

PFAS are prevalent in many industries, and so is the human reliance on essential products that contain PFAS, such as computers and lithium-ion batteries. One of the most problematic PFAS-containing products in terms of environmental contamination has historically been aqueous film forming foam, or AFFF, which was used for firefighting at airports and in the military; it’s made of PFOA and PFOS. When you spray AFFF onto a liquid, it moves to the surface and extinguishes the fire by preventing oxygen from getting to it. But, when used it can seep into soil and groundwater. AFFF has been used in the United States and worldwide for decades, largely by the military and aviation industry.  Recently, both government and industry started examining PFAS-free substitutes. Alternatives, however, do not exist in many applications and are hard to find or perform less effectively.

Although electron beams are very effective at breaking down entire suites of PFAS compounds, not every compound has been tested so far. The researchers found that all of the PFAS compounds the U.S. Environmental Protection Agency is currently considering regulating in drinking water were effectively destroyed by electron beam technology. But there may be types of PFAS an electron beam cannot destroy.

Research continues on several fronts to find alternatives to PFAS. At the same time, leaders in science and industry will continue to search for and enhance methods to eradicate these forever chemicals in the environment. Fermilab and its electron-beam technology stand at the forefront of this research.

This work is supported by the Office of Energy Efficiency and Renewable Energy of the U.S. Department of Energy Office of Science and 3M.

Fermi National Accelerator Laboratory is supported by the Office of Science of the U.S. Department of Energy. The Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov.

Since the 1960s, scientists have discovered more than a dozen fundamental particles. They all have fit perfectly into the theoretical framework known as the Standard Model, the best description physicists have of the subatomic world. The Higgs boson, which was co-discovered by the CMS and ATLAS experiments at the Large Hadron Collider at CERN in 2012, was the last fundamental particle predicted by the Standard Model. Despite this major discovery, scientists still have many questions about the fundamental building blocks of the universe. Researchers know that the Standard Model is incomplete and cannot explain many physical phenomena—dark matter being a notable example.

Scientists around the world are pushing the Standard Model’s limits and are searching for new particles that can help explain outstanding questions about the inner workings of the universe.

“We’re in the business of finding new particles,” said Cristian Peña, the convener of the CMS exotic particles group and scientist at the U.S. Department of Energy’s Fermi National Accelerator Laboratory. “That’s what we’re here for.”

Peña and other scientists at Fermilab recently collaborated with their international colleagues on CMS to create a new tool that is allowing them to scout for particles that can travel around one to ten meters before decaying into more stable byproducts. Now scientists are analyzing the new dataset produced by this tool. According to Peña, they will either find new physics, or set the most stringent limits in the search for long-lived particles: a class of theoretical particles that can travel deep into the detector before creating visible signals.

“Our data set is no longer doubling every six months like it did at the very beginning of the program,” says Sergo Jindariani, a senior scientist at Fermilab. “The places where we could still make quick discoveries is where we haven’t looked before, and long-lived particles are an example of that.”

When scientists built the experiments for the LHC, they assumed that new particles would behave like those they had discovered in the past and decay very quickly. For example, the top quark, which was discovered at Fermilab in 1995, has a lifetime of roughly 5×10⁻²⁵ seconds. This is so short that top quarks decay before they can move the length of a hydrogen atom. But now more and more scientists are questioning this assumption.

“We’ve looked everywhere and come up empty so far,” said Peña. “We know we can do better by using the lifetime of the particles.”

Scientists already know that particles have a wide range of lifetimes. For instance, bottom quarks can travel a few millimeters before they decay, and muons can travel a few hundred meters. Today, scientists are asking, what if there are new particles that fall somewhere in-between?

Even if these long-lived particles are extremely rare, CMS will still have a good shot of seeing them if they are being produced by the LHC.

“The CMS muon system has a lot of material, so if long-lived particles are decaying inside our detector, we should see a particle shower in the muon chambers,” said Peña. “The signature is very powerful.”

But the question was whether scientists can find these unexpected particle showers hiding in their data. The LHC produces about a billion proton-proton collisions every second. Because more than 99.99% of the collisions generate particles and physical phenomena that are uninteresting, scientists use data-sorting devices called triggers. Triggers pick the top 0.01% of events to be processed and stored within the Worldwide LHC Computing Grid and discard the rest.

“CMS is an extremely successful detector,” said Jindariani. “It really does the physics it was designed to do. But long-lived particles were not something people had in mind when they were designing the CMS trigger system.”

The team realized that if they wanted to improve their chances of finding long-lived particles with the CMS experiment, they would need to update the CMS trigger to look for the striking and peculiar signature these particles are expected to leave behind in the detector.

“With a dedicated trigger, we saw that we could gain an order of magnitude in the sensitivity of these searches,” Jindariani said.

But updating the trigger is always a complicated endeavor. It required help and expertise from researchers and engineers throughout the CMS collaboration. Jindariani pointed out that the trigger system relies on numerous data streams from different parts in the detector. These data streams operate like roads in a city and allow the data to flow from the outer most parts of the detector into the “downtown” processing center, where the data is compiled and quickly evaluated by algorithms. Adding a new data stream is like adding a bike lane into an already bustling metropolitan area.

“It would need to co-exist with other triggers,” Jindariani said. “That’s a delicate play; we don’t want to damage what’s already in place.”

After extensive analysis of the CMS trigger and discussions with the collaboration, the team realized it was possible, thanks to a few unused bits left over from the original design. But then came the challenge of actually implementing their new trigger in the data processing of the experiment.

“Once everybody was onboard with the conceptual implementation, we needed to go into the firmware and software,” Jindariani said.

Firmware provides basic machine instructions that allow the hardware—in this case, Field Programmable Gate Arrays—to function according to the programmed algorithm. FPGAs can be very fast but are often not very dynamic.

“FPGAs have a limited amount of processing power, and the CMS trigger algorithms are pretty resource-hungry,” Jindariani said. “We needed to be clever in order to not overwhelm the FPGAs’ capabilities.”

Since the LHC makes protons collide every 25 nanoseconds, their new trigger also had to be fast.

“We’re locked into time slices,” Jindariani said. “The algorithm needs to be executed within a few hundred nanoseconds. If it takes longer, it’s not good enough. This work was only possible through a strong team of scientists and engineers working together.”

Even after the challenges of resource management and timing were solved, the team still had to address a few unexpected hiccups. During the testing phase, they saw that the trigger was activated during every collision. After further analysis, they found this was because the transmitter on one of the muon systems was malfunctioning.

“This was a problem that had existed before, but the other triggers didn’t see it because they weren’t looking for it,” Jindariani says.

Once all the glitches were ironed out, the trigger evaluated all the LHC collisions happening within the CMS detector between 2022 and 2023 — around 10¹⁶, or 10 million billion — and collected a dataset with around 10⁸ events. Scientists are currently analyzing this new data set and hope to have their first results this summer.

“This trigger is one of the big innovations within CMS,” Peña says. “We’ll either find new particles, or — if nature doesn’t want it that way — we will set more stringent limits on long-lived particles.”

Fermi National Accelerator Laboratory is supported by the Office of Science of the U.S. Department of Energy. The Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov.