The Large Hadron Collider is an enormous particle accelerator whose 17-mile tunnel straddles the borders of France and Switzerland. A group of physicists at the University of Nevada, Reno has analyzed data from the accelerator that could ultimately prove or disprove the possibility of a fifth force of nature.
As the largest science instrument ever built, the LHC has the science community buzzing with excitement as it may help in understanding the inner workings of Nature.
Remarkably, some of the new physics that may be studied at this $6 billion facility can be probed using low-cost experiments fitting in a typical laboratory room.
In a forthcoming Physical Review Letter article, the University of Nevada, Reno physicists are reporting an analysis of an experiment on violation of mirror symmetry in atoms. Their refined analysis sets new limits on a hypothesized particle, the extra Z-boson, carving out the lower-energy part of the discovery reach of the LHC.
Andrei Derevianko, an associate professor in the College of Science's Department of Physics, who has conducted groundbreaking research to improve the time-telling capabilities of the world's most accurate atomic clocks, is one of the principals behind what is believed to be the most accurate to-date low-energy determination of the strength of the electroweak coupling between atomic electrons and quarks of the nucleus.
Derevianko and his colleagues have determined the coupling strength by combining previous measurements made by Dr. Carl Wieman, a Nobel laureate in physics, with high-precision calculations in a cesium atom.
The original work by Wieman used a table-top apparatus at the University of Colorado in Boulder, Colo. The Boulder team monitored a "twinge" of weak force in atoms, which are otherwise governed by the electromagnetic force. The Standard Model of elementary particles, developed in the early 1970s, holds that heavy particles, called Z-bosons, carry this weak force. In contrast to the electromagnetic force, the weak force violates mirror symmetry: an atom and its mirror image behave differently. This is known to physicists as "parity violation."
The Boulder group's experiment opened the door to new inquiry, according to Derevianko.
"It pointed out a discrepancy, and hinted at a possibility for new physics, in particular, extra Z-bosons," he said.
Interpretation of the Boulder experiment requires theoretical input. The analysis requires detailed understanding of the correlated motion of 55 electrons of cesium atom. This is not an easy task as the number of memory units required for storing full quantum-mechanical wavefunctions exceeds the estimated number of atoms in the Universe. Special computational tools and approximations were developed. Compared to previous analyses, reaching the next level of accuracy required a factor of 1,000 increase in computational complexity.
The paper represents a dramatic improvement as researchers have struggled to develop a more precise test of the Standard Model. Derevianko's group, which included Dr. S. Porsev and a number of students, has worked on the analysis of the Boulder experiment for the past eight years.
"Finally, the computer technology caught up with the number-crunching demands of the problem and we were able to attack the problem," says Derevianko. "I have greatly benefited from collaborations in this complex problem. A fellow co-author, Kyle Beloy, for example, has recently been recognized as an Outstanding Graduate Researcher by the University."
In contrast to previous, less accurate interpretations of the Boulder experiment, Derevianko's group has found a perfect agreement with the prediction of the Standard Model. This agreement holds important implications for particle physics.
"Atomic parity violation places powerful constraints on new physics beyond the Standard Model of elementary particles," Derevianko said. "With this new-found precision, we are doing a better job of 'listening' to the atoms."
By refining and improving the computations, Derevianko said there is potential for a better understanding of hypothetical particles (extra Z-bosons) which could be carriers of a so-far elusive fifth force of nature. For years, physics researchers have grappled with experiments to prove or disprove the possibility of a fifth force of Nature.
There are four known fundamental forces of Nature. In addition to gravity, electromagnetism creates light, radio waves and other forms of radiation. Two other forces operate only on an atomic level: These are the strong force, which binds particles in the nucleus, and the weak force, which reveals itself when atoms break down in radioactive decay, or as in the Boulder experiment, through the parity violation.
The possibility of a fifth force could dispute the long-held belief that the force of gravity is the same for all substances.
"New physics beyond the Standard Model is the next frontier," Derevianko said, "and it's the theoretical motivation for much of this research."
To read Derevianko's paper, go to: http://arxiv.org/abs/0902.0335
The following is a summary of Derevianko's paper, which is entitled, "Precision determination of electroweak coupling from atomic parity violation and implications for particle physics":
Atomic parity violation places powerful constraints on new physics beyond the Standard Model of elementary particles. The measurements are interpreted in terms of the nuclear weak charge, quantifying the strength of the electroweak coupling between atomic electrons and quarks of the nucleus. We report the most accurate to-date determination of this coupling strength by combining previous measurements by the Boulder group with our high-precision calculations in cesium atom. Our result is in a perfect agreement with the prediction of the Standard Model.
In combination with the results of high-energy collider experiments, our work confirms the predicted energy dependence (or ``running'') of the electroweak interaction over an energy range spanning four orders of magnitude (from ~10 MeV to ~100 GeV) and places new limits on the masses of extra Z bosons (Z'). Our raised bound on the Z' masses carves out a lower-energy part of the discovery reach of the Large Hadron Collider. At the same time, a major goal of the LHC is to find evidence for supersymmetry (SUSY), one of the basic, yet experimentally unproven, concepts of particle physics. Our result is consistent with the R-parity conserving SUSY with relatively light (sub-TeV) superpartners. This raises additional hopes of discovering SUSY at the LHC.
Mike Wolterbeek | EurekAlert!
Further reports about: > LHC > Large Hadron Collider > Nature Immunology > Z-boson > atomic electrons > computational tools > electromagnetic force > elementary particles > high-precision calculations > hypothetical particles > parity violation > quantum-mechanical wavefunctions > quarks of the nucleus
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