Over the weekend, the world’s most powerful particle accelerator began its second act.
After two years of upgrades and repairs, proton beams once again circulated around the Large Hadron Collider, located at the CERN laboratory near Geneva, Switzerland.
It’s an important and exciting project for scientists and students in the Northern Illinois University physics department and the more than 1,700 U.S. scientists who work on LHC experiments. They are prepared to join thousands of their international colleagues to study the highest-energy particle collisions ever achieved in the laboratory.
These collisions – hundreds of millions of them every second – will lead scientists to new and unexplored realms of physics, and could yield extraordinary insights into the nature of the physical universe.
A highlight of the LHC’s first run, which began in 2009, was the discovery of the Higgs boson, the last in the suite of elementary particles that make up scientists’ best picture of the universe and how it works. The discovery of the Higgs was announced in July 2012 by two experimental collaborations, ATLAS and CMS. Continuing to measure the properties of the Higgs will be a major focus of LHC Run 2.
“The Higgs discovery was one of the most important scientific achievements of our time,” said James Siegrist, the U.S. Department of Energy’s associate director of science for high energy physics. “With the LHC operational again, at even higher energies, the possibilities for new discoveries are endless, and the United States will be at the forefront of those discoveries.”
Dhiman Chakraborty
Since joining ATLAS in 2007, the NIU team, led by physics professor Dhiman Chakraborty, has contributed to a number of critical aspects of the project.
“The NIU team members continue to shoulder key responsibilities in monitoring and certifying the quality of data taken with the Tile Hadronic Calorimeter (TileCal),” Chakraborty said. “This component of the ATLAS detector is essential in measuring the energies of many particles that are created from the enormous energy of each collision event, with particles traveling outward in all directions at speeds approaching that of light.”
NIU also has the full responsibility to ensure that the results of daily calibration of the entire TileCal are properly stored and available at all times, so as to deliver the most accurate measurements.
Another critical project where NIU has been active is the ATLAS Fast Tracker (FTK) upgrade.
Team members have contributed to understanding performance expectations and algorithm optimizations leading to the realization of the FTK, which is set to afford vast improvements in ATLAS’s capability to take cleaner data in the upcoming run of the LHC. Professor Jahred Adelman, who joined NIU in fall 2014, is in charge of simulation of the FTK, which is designed, built and operated by 13 institutions, including five from the United States.
Members of the NIU team also have been deeply involved in and contributed extensively to analyses of proton-proton collision data collected by ATLAS in search of signs of physical phenomena and laws yet to be discovered. So far, three NIU graduate students have earned their Ph.D. degrees studying production and decay of top quarks and heavy gauge bosons – processes that have a high probability of revealing such signals in a wide range of scenarios.
Two other graduate students, Blake Burghgrave and Puja Saha, are currently engaged in studies of the Higgs sector. Additional members of ATLAS team from NIU include senior research scientist Yuri Smirnov and post-doctoral research associate Nancy Andari.
“We are engaged in a program of research aimed at gaining a deeper insight into the Higgs sector, which may well turn out to have a structure richer than what has been revealed so far,” Chakraborty said. “The NIU team is focusing particularly on the deep connection between the top quark and the Higgs boson. This is one of the highest priorities on the physics charter for the upcoming run of the LHC.”
The NIU ATLAS effort has attracted more than $2 million in federal funding already, in addition to external funding through collaborative partnerships with other institutions.
During the LHC’s second run, particles will collide at a staggering 13 teraelectronvolts (TeV), which is 60 percent higher than any accelerator has achieved before. The LHC’s four major particle detectors – ATLAS, CMS, ALICE and LHCb – will collect and analyze data from these collisions, allowing them to probe new areas of research that were previously unattainable.
At 17 miles around, the Large Hadron Collider is one of the largest machines ever built. The United States played a vital role in the construction of the LHC and the huge and intricate detectors for its experiments. Seven national laboratories joined roughly 90 U.S. universities to build key components of the accelerator, detectors and computing infrastructure, with funding from the DOE Office of Science and the National Science Foundation (NSF).
The U.S. contingent was part of an estimated 10,000 people from 113 different countries who helped to design, build and upgrade the LHC accelerator and its four particle detectors.
“We are on the threshold of an exciting time in particle physics. The LHC will turn on with the highest energy beam ever achieved,” said Fleming Crim, NSF assistant director for mathematical and physical sciences. “This energy regime will open the door to new discoveries about our universe that were impossible as recently as two years ago.”
In addition to the scientists pushing toward new discoveries on the four main experiments, the U.S. provides a significant portion of the computing and data analysis – roughly 23 percent for ATLAS and 33 percent for CMS.
U.S. institutions will continue to make important contributions to the LHC and its experiments, even beyond the second run, which is scheduled to continue through the middle of 2018. Universities and national laboratories are developing new accelerator and detector technology for future upgrades of the LHC and its experiments. This ongoing work encourages a strong partnership between science and industry, and drives technological innovation.
“Operating accelerators for the benefit of the physics community is what CERN’s here for,” CERN Director General Rolf Heuer said. “Today, CERN’s heart beats once more to the rhythm of the LHC.”
More information on the U.S. role in the Large Hadron Collider is available online, as is a series of videos on the LHC featuring U.S. scientists.
