A group of 50 international physicists, led by UC Riverside’s Ann Heinson, has detected for the first time a subatomic particle, the top quark, produced without the simultaneous production of its antimatter partner – an extremely rare event. The discovery of the single top quark could help scientists better explain how the universe works and how objects acquire their mass, thereby assisting human understanding of the fundamental nature of the universe.
The heaviest known elementary particle, the top quark has the same mass as a gold atom and is one of the fundamental building blocks of nature. Understood to be an ingredient of the nuclear soup just after the Big Bang, today the top quark does not occur naturally but must be created experimentally in a high-energy particle accelerator, an instrument capable of recreating the conditions of the early universe.
“We’ve been looking for single top quarks for 12 years, and until now no one had seen them,” said Heinson, a research physicist in the Department of Physics and Astronomy. “The detection of single top quarks – we detected 62 in total – will allow us to study the properties of top quarks in ways not accessible before. We are now able to study how the top quark is produced and how it decays. Do these happen as theory says they should" Are new particles affecting what we see" We're now better positioned to answer such questions.”
The detection of the top quark on its own was the outcome of a time-consuming process involving hundreds of scientists who constitute the “DZero” collaboration, a team of experimenters studying the top quark in particle collisions.
For its part, Heinson’s team first collected data from collision experiments conducted between 2002 and 2005 at the Tevatron Collider, the world’s highest energy particle accelerator that is comprised of a four-mile long underground ring at the Department of Energy’s Fermi National Accelerator Laboratory in Batavia, Ill. The collisions recorded were those between protons and antiprotons (the antimatter counterparts of protons).
Next, Heinson and her colleagues analyzed the record of high-energy collisions using powerful computers that helped the researchers determine which types of particles resulted from the collisions.
When a proton smashes head-on into an antiproton at nearly the speed of light, the collision occasionally produces a top quark. This heavy, unstable particle exists, however, for only a tiny fraction of a second before it decays into lighter particles, thereby complicating its detection. Physicists therefore must look at the top quark's descendents to identify it.
“We detected the top quark using the electronic signature of its decay products,” said Heinson, the primary author of a research paper on the single top quark’s detection that her group will submit to Physical Review Letters. “We measured the position of charged particles using a silicon vertex detector, which is an instrument – first encountered by the particles after the collision – that can precisely reconstruct the trajectories of charged particles. Since theory predicts single top quark production, we knew what to look for. It was extremely difficult, however, to find.”
In the near future, Heinson’s team plans to analyze more data generated by the Tevatron and also work with a new particle accelerator – the Large Hadron Collider – being built on the outskirts of Geneva, Switzerland, and scheduled to begin operation at the end of 2007.
Iqbal Pittalwala | EurekAlert!
Climate cycles may explain how running water carved Mars' surface features
02.12.2016 | Penn State
What do Netflix, Google and planetary systems have in common?
02.12.2016 | University of Toronto
A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.
Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...
In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.
“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...
The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.
The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...
Broadband rotational spectroscopy unravels structural reshaping of isolated molecules in the gas phase to accommodate water
In two recent publications in the Journal of Chemical Physics and in the Journal of Physical Chemistry Letters, researchers around Melanie Schnell from the Max...
The efficiency of power electronic systems is not solely dependent on electrical efficiency but also on weight, for example, in mobile systems. When the weight of relevant components and devices in airplanes, for instance, is reduced, fuel savings can be achieved and correspondingly greenhouse gas emissions decreased. New materials and components based on gallium nitride (GaN) can help to reduce weight and increase the efficiency. With these new materials, power electronic switches can be operated at higher switching frequency, resulting in higher power density and lower material costs.
Researchers at the Fraunhofer Institute for Solar Energy Systems ISE together with partners have investigated how these materials can be used to make power...
16.11.2016 | Event News
01.11.2016 | Event News
14.10.2016 | Event News
02.12.2016 | Medical Engineering
02.12.2016 | Agricultural and Forestry Science
02.12.2016 | Physics and Astronomy