A milestone achieved in the discovery of the fundamental forces of the universe at the Large Hadron Collider

Researchers at the University of Rochester, working with the CMS Collaboration on CERNhave made significant advances in measuring the electroweak mixing angle, increasing our understanding of the Standard Model of particle physics.

Their work helps explain the fundamental forces of the universe, supported by experiments like those conducted at the Large Hadron Collider, which delve into conditions similar to those behind Big Bang.

Uncovering Universal Mysteries

In the quest to decipher the mysteries of the universe, researchers from the University of Rochester have been involved for decades with international collaborations at the European Organization for Nuclear Research, more commonly known as CERN.

Building on their extensive involvement at CERN, particularly within the CMS (Compact Muon Solenoid) collaboration, the Rochester team, led by Arie Bodek, the George E. Pake Professor of Physics, recently achieved a breakthrough . Their achievement centers on measuring the electroweak mixing angle, a core component of the Standard Model of Particle Physics. This model describes how particles interact and accurately predicts a plethora of phenomena in physics and astronomy.

“Recent measurements of the electroweak mixing angle are extremely precise, calculated from proton collisions at CERN, and strengthen our understanding of particle physics,” says Bodek.

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 Rochester group in the CMS Collaboration includes principal investigators Regina Demina, a professor of physics, and Aran Garcia-Bellido, an associate professor of physics, along with postdoctoral research associates and graduate and undergraduate students.

A legacy of discovery and innovation at CERN

Located in Geneva, Switzerland, CERN is the world’s largest particle physics laboratory, known 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 key roles in the 2012 discovery of the Higgs boson – an elementary particle that helps explain the origin of mass in the universe.

The collaborative work involves collecting and analyzing data collected by the Solenoid Compact Muon 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 accelerator structures built underground and straddling the border between Switzerland and France.

The main goal of the LHC is to explore the fundamental building blocks of matter and the forces that drive them. It achieves this by accelerating beams of protons or ions to roughly the speed of light and slamming them into each other 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 the behavior of particles under extreme conditions.

Unification of the Unified Forces

In the 19th century, scientists discovered that the various forces of electricity and magnetism were related: a changing electric field produces a magnetic field and vice versa. The discovery formed the basis of electromagnetism, which describes light as waves and explains many phenomena in optics, along with 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. The weak force acts within the nucleus of atoms and is responsible for processes such as radioactive decay and powering the sun’s energy production. This discovery led to the development of the electroweak theory, which posits that electromagnetism and the weak force are actually low-energy manifestations of a unified force called the unified electroweak interaction. Major discoveries, such as the Higgs boson, have confirmed this concept.

Advances in the Electroweak Interaction

The CMS collaboration recently performed one of the most precise measurements yet of this theory, analyzing billions of proton-proton collisions at the LHC at CERN. Their focus was on measuring the weak mixing angle, a parameter that describes how electromagnetism and the weak force mix together to create particles.

Previous measurements of the weak mixing angle have sparked debate within 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 applied new techniques to minimize the systematic uncertainties inherent in this measurement, increasing its accuracy.

Understanding the weak mixing angle sheds light on how different forces in the universe work together at the smallest scales, deepening an 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 applying them to the Large Hadron Collider,” says Bodek. “These new techniques have heralded a new era of tests of the accuracy of Standard Model predictions.”

The CMS Collaboration is an international scientific collaboration responsible for the Compact Muon Solenoid (CMS) experiment at CERN’s Large Hadron Collider. Comprised of over 4,000 scientists from more than 200 institutions and 50 countries, the CMS Collaboration conducts research in high-energy physics, exploring fundamental particles and forces, including the famous discovery of the Higgs boson in 2012.