Events on March 2 in history

Researchers at Fermilab announce the discovery of the top quark.

Discovering the Universe's Secrets at Fermilab

Nestled just outside Batavia, Illinois, a short drive from the bustling metropolis of Chicago, lies the Fermi National Accelerator Laboratory, more commonly known as Fermilab. This distinguished institution serves as a national laboratory for the United States Department of Energy, acting as a global hub for high-energy particle physics. Since 2007, Fermilab has been expertly managed by the Fermi Research Alliance, a collaborative endeavor between the esteemed University of Chicago and the Universities Research Association (URA), firmly establishing its place within the vibrant Illinois Technology and Research Corridor.

The Legacy of the Tevatron and Future Accelerators

For decades, Fermilab was home to the truly groundbreaking Tevatron particle accelerator, an engineering marvel that, until the Large Hadron Collider (LHC) powered up near Geneva, Switzerland, in 2008, held the title of the most powerful particle accelerator on Earth. The Tevatron could propel protons and antiprotons to incredible energies of 980 GeV and orchestrate proton-proton collisions reaching up to 1.96 TeV, making it the very first accelerator to achieve the elusive one "tera-electron-volt" energy level. With a circumference spanning 3.9 miles (6.3 km), it was the world's fourth-largest accelerator of its kind. Its most celebrated triumph came in 1995 with the historic discovery of the top quark, announced by research teams utilizing the Tevatron's sophisticated CDF and DØ detectors. After years of invaluable service, the Tevatron gracefully concluded its operations in 2011.

Today, Fermilab's most potent operational accelerator is the Main Injector, a substantial two-mile (3.3 km) circumference ring that continues to push the boundaries of particle physics. Looking towards the future, construction for the innovative PIP-II linear accelerator commenced in 2020, promising new capabilities and discoveries.

Probing the Invisible: Neutrino and Quantum Experiments

Fermilab is a global leader in exploring the mysteries of the universe's most elusive particles, hosting a suite of cutting-edge neutrino experiments. Current active projects include MicroBooNE (Micro Booster Neutrino Experiment), ICARUS (Imaging Cosmic and Rare Underground Signals), NOνA (NuMI Off-Axis νe Appearance), and Muon g-2, each designed to shed light on the fundamental properties of neutrinos. The laboratory has also seen the successful completion of significant neutrino experiments such as MINOS (Main Injector Neutrino Oscillation Search), MINOS+, MiniBooNE, and SciBooNE (SciBar Booster Neutrino Experiment), alongside the SeaQuest fixed-target experiment.

The scale of these experiments is truly impressive; for instance, the MiniBooNE detector comprised a massive 40-foot (12 m) diameter sphere, filled with 800 tons of mineral oil and meticulously lined with 1,520 phototube detectors, recording an astounding estimated one million neutrino events annually. SciBooNE, sharing the same neutrino beam as MiniBooNE, offered advanced fine-grained tracking capabilities. A remarkable aspect of experiments like NOνA and MINOS is their use of Fermilab's NuMI (Neutrinos at the Main Injector) beam, an incredibly intense stream of neutrinos that travels an astonishing 455 miles (732 km) directly through the Earth to remote detectors located in the Soudan Mine and Ash River, Minnesota. Demonstrating its ongoing commitment to international collaboration and cutting-edge research, the ICARUS neutrino experiment was painstakingly moved from CERN to Fermilab in 2017, with operations planned to commence in 2020.

Beyond neutrinos, Fermilab is also at the forefront of quantum information science. The laboratory established the Fermilab Quantum Institute in 2019 and, since 2020, proudly houses the SQMS (Superconducting Quantum and Materials Science) center, aiming to harness the bizarre rules of quantum mechanics for future technologies.

Fermilab in the Public Eye: Science, Culture, and Nature

More than just a scientific powerhouse, Fermilab also plays an important role in the public sphere. The site is home to a thriving native prairie ecosystem restoration project, offering a glimpse into the natural beauty of Illinois. It also serves as a vibrant cultural center, regularly hosting a variety of events for the community, from enlightening public science lectures and symposia to captivating classical and contemporary music concerts, lively folk dancing, and engaging arts galleries. Under normal circumstances, the entire site is open to visitors from dawn to dusk, requiring only valid photo identification for entry. However, like many public institutions worldwide, access has been temporarily restricted since March 2020 due to the global COVID-19 pandemic. The laboratory's significant contributions to science have even been recognized in the cosmos, with asteroid 11998 Fermilab bearing its name.

The Enigmatic Top Quark: A Giant Among Particles

Among the pantheon of elementary particles, the top quark, sometimes affectionately referred to as the "truth quark" (symbol: t), stands out as the most massive of all observed. This incredible mass originates from its profound coupling to the Higgs Boson. This coupling, denoted as y_t, is remarkably close to unity, making it the largest (and strongest) coupling within the Standard Model of particle physics at and above the scale of weak interactions. As previously mentioned, the top quark's existence was definitively confirmed in 1995 by the CDF and DØ experiments right here at Fermilab.

Like all its quark relatives, the top quark is a fermion, possessing a spin of 1/2, and actively participates in all four fundamental interactions that govern the universe: gravitation, electromagnetism, weak interactions, and strong interactions. It carries an electric charge of +2/3 e and boasts an astonishing mass of 172.76 ± 0.3 GeV/c², a value surprisingly close to that of a rhenium atom. Its antimatter counterpart is the top antiquark (symbol: t), often called the antitop quark or simply antitop, which shares all its properties but with opposite signs for charge and other quantum numbers.

The top quark primarily interacts with gluons, the carriers of the strong force, and is typically produced in powerful hadron colliders through this interaction. However, once forged, the top (or antitop) has a singular path to decay: via the weak force. It rapidly transforms into a W boson and almost always a bottom quark, though on rarer occasions, it might decay into a strange quark or, in the rarest instances, a down quark.

The Standard Model predicts the top quark's mean lifetime to be incredibly short, roughly 5 x 10^-25 seconds. This fleeting existence is about twenty times shorter than the timescale for strong interactions, meaning the top quark doesn't live long enough to "hadronize" – that is, it doesn't combine with other quarks to form composite particles called hadrons. This unique characteristic offers physicists an unparalleled opportunity to study a "bare" or unadorned quark, a feat impossible with any other quark, all of which invariably hadronize before they can be directly observed in their fundamental state.

Because of its immense mass, the top quark's properties provided crucial indirect evidence for determining the mass of the Higgs boson. Consequently, the characteristics of the top quark are meticulously studied as a vital tool to differentiate between various competing theories of new physics that aim to extend beyond the current Standard Model. Its remarkably short lifetime, decaying faster than the hadronization time, also makes the top quark the only quark that has been directly observed.

FAQs about Fermilab and the Top Quark

What is Fermilab?

Fermilab (Fermi National Accelerator Laboratory) is a United States Department of Energy national laboratory specializing in high-energy particle physics, located near Chicago, Illinois.

Who operates Fermilab?

Since 2007, Fermilab has been operated by the Fermi Research Alliance, a joint venture between the University of Chicago and the Universities Research Association (URA).

What was the Tevatron?

The Tevatron was a landmark particle accelerator at Fermilab, which until 2008, was the most powerful in the world. It was instrumental in the discovery of the top quark and was shut down in 2011.

What is the Top Quark?

The top quark is the most massive of all observed elementary particles. It's a fundamental constituent of matter, discovered at Fermilab in 1995, and its unique properties offer insights into the Higgs boson and new physics theories.

Why is the Top Quark important?

Its extreme mass and incredibly short lifetime prevent it from forming hadrons, allowing scientists to study a "bare" quark directly. Its properties were crucial for indirectly determining the mass of the Higgs boson and are used to test theories beyond the Standard Model.

What kind of research does Fermilab conduct today?

Today, Fermilab continues extensive research in high-energy particle physics, focusing on neutrino experiments (like MicroBooNE, ICARUS, NOνA), muon experiments (Muon g-2), and quantum information science through initiatives like the Fermilab Quantum Institute and the SQMS center.

Can the public visit Fermilab?

Ordinarily, Fermilab is open to the public from dawn to dusk for visitors with valid photo identification. However, public access has been temporarily suspended since March 2020 due due to the COVID-19 pandemic.