Building on their strong involvement at CERN, the University of Rochester team recently made “incredibly precise” measurements of the electroweak mixing angle, a crucial part of the Standard Model of particle physics. Credit: Samuel Joseph Hertzog; Julien Marius Ordan
Researchers from the University of Rochester, working with the CMS Collaboration at
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Their work helps explain the fundamental forces of the universe, supported by experiments such as those at the Large Hadron Collider, which explore conditions similar to those following the fall of the Earth.
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Unveiling universal mysteries
In their quest to decode the mysteries of the universe, researchers at the University of Rochester have participated for decades in international collaborations within the European Organization for Nuclear Research, more commonly known as CERN.
Building on its considerable commitment to CERN, including the Compact Muon Solenoid (CMS) collaboration, the Rochester team, led by Arie Bodek, George E. Pake Professor of Physics, recently reached a milestone. His achievement concerns the measurement of the electroweak mixing angle, a crucial element of the standard model of particle physics. This model describes how particles interact and accurately predicts a multitude of phenomena in physics and astronomy.
“Recent measurements of the electroweak mixing angle are incredibly precise, calculated from proton collisions at CERN, and strengthen the understanding of particle physics,” Bodek says.
The CMS collaboration brings together members of the particle physics community from around the world to better understand the fundamental laws of the universe. In addition to Bodek, the CMS collaboration’s Rochester cohort includes principal investigators Regina Demina, professor of physics, and Aran Garcia-Bellido, associate professor of physics, as well as postdoctoral research associates and graduate and undergraduate students .
University of Rochester researchers have long worked at CERN as part of the Compact Muon Solenoid (CMS) collaboration, and were instrumental in the discovery of the Higgs boson in 2012. Credits: Samuel Joseph Hertzog; Julien Marius Ordan
A legacy of discovery and innovation at CERN
Located in Geneva, Switzerland, CERN is the world’s largest particle physics laboratory, renowned for its groundbreaking discoveries and cutting-edge experiments.
Rochester researchers have a long history of working at CERN as part of the CMS collaboration, including playing a key role in the 2012 discovery of the Higgs boson, an elementary particle that helps explain the origin of mass in the universe.
The collaboration’s work involves collecting and analyzing data gathered by the compact muon solenoid detector at CERN’s Large Hadron Collider (LHC), the world’s largest and most powerful particle accelerator. The LHC consists of a 17-mile ring of superconducting magnets and accelerating structures built underground and spanning the border between Switzerland and France.
The LHC’s main goal is to explore the fundamental building blocks of matter and the forces that govern them. It does this by accelerating beams of protons or ions to nearly the speed of light and smashing them together at extremely high energies. These collisions recreate conditions similar to those that existed fractions of a second after the Big Bang, allowing scientists to study how particles behave under extreme conditions.
Untangling unified forces
In the 19th century, scientists discovered that the different forces of electricity and magnetism were linked: a changing electric field produces a magnetic field and vice versa. This discovery forms the basis of electromagnetism, which describes light as a wave and explains many optical phenomena, while describing how electric and magnetic fields interact.
Building on this understanding, physicists in the 1960s discovered that electromagnetism is related to another force, the weak force. This force operates in the nuclei of atoms and is responsible for processes such as radioactive decay and powering solar energy production. This revelation led to the development of electroweak theory, which posits that electromagnetism and the weak force are actually low-energy manifestations of a unified force called the unified electroweak interaction. Key discoveries, such as the Higgs boson, have confirmed this concept.
Advances in electroweak interaction
The CMS collaboration recently made one of the most precise measurements of this theory to date, analyzing billions of proton-proton collisions at CERN’s LHC. Their goal was to measure the weak mixing angle, a parameter describing how electromagnetism and the weak force mix to create particles.
Previous measurements of the electroweak mixing angle have sparked debate in the scientific community. However, the latest findings closely match predictions from the Standard Model of particle physics. Rochester graduate student Rhys Taus and postdoctoral research associate Aleko Khukhunaishvili implemented new techniques to minimize the systematic uncertainties inherent in this measurement, improving its accuracy.
Understanding the weak mixing angle provides insight into how the different forces in the universe work together at the smallest scales, thereby deepening understanding of the fundamental nature of matter and energy.
“The Rochester team has been developing innovative techniques and measuring these electroweak parameters since 2010, and then implementing them at the Large Hadron Collider,” Bodek says. “These new techniques have ushered in a new era of testing the accuracy of Standard Model predictions.”