Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

JLab’s CLAS physicists learn a little more about ‘nothing,’ get thrown for a spin

03.07.2003


Daniel S. Carman (Ohio University) and nearly 150 members of Jefferson Lab’s CLAS Collaboration studied the spin transfer from a polarized electron beam to a produced Lambda particle. Their results were recently published in Physical Review Letters.



Measurements taken using Jefferson Lab’s CEBAF Large Acceptance Spectrometer (CLAS) are telling us more about how matter is produced from "nothing," that is, the vacuum.
Using the CLAS in Hall B, Daniel S. Carman of Ohio University and nearly 150 members of the CLAS Collaboration studied the spin transfer from a polarized electron beam to a produced Lambda particle. Their results were recently published in Physical Review Letters.

The CLAS experimenters collided JLab’s polarized electron beam into a proton target, producing a polarized Lambda (?0) and a kaon (K+). Physicists have long known that matter and anti-matter can be created when energetic particles strike one another. The new particles are not really created from "nothing." They are created from the available kinetic energy of the colliding particles. Visualize a bowling ball hitting its rack of 10 pins so hard that the 10 pins turn into 11 normal pins and one "anti-pin." Energy is conserved and so is matter; that’s why a new anti-matter particle is created each time a matter particle is created.



In a simple quark model of the reaction dynamics, a circularly polarized virtual photon strikes an oppositely polarized up quark inside the proton . The spin of the struck quark flips in direction and the quark recoils from its neighbors, stretching a flux-tube of gluonic matter between them. When the stored energy in the flux-tube is sufficient, the tube is "broken" by production of a strange quark-antiquark pair. Using this simple picture, the researchers could explain the angular dependence of the Lambda polarization if the quark pair was produced with the spins in opposite directions, or anti-aligned.

Putting the right spin on it

These anti-aligned spins could throw theorists into a spin. According to the popular triplet-P-zero (3P0) model, a quark-antiquark pair is produced with vacuum quantum numbers, and that means their spins should be aligned. These results imply that the 3P0 model may not be as widely applicable as was thought.

Winston Roberts, a theorist at Jefferson Lab and associate professor of physics at Old Dominion University, finds the CLAS measurement very interesting. "If they are right, it means we have to rethink what we thought we understood about our models for baryon decays," he says. "The CLAS results may also be saying something about what we understand of baryons themselves -- our knowledge of how to describe scattering processes such as the one they measure, or even that there may be oddities, peculiarities, dare I say ’strangeness,’ in the way strange quark-antiquark pairs are produced."

The experimenters expect further reaction from theorists. "Polarized Lambda production is obviously sensitive to the spin-dynamics of quark-pair creation," says Mac Mestayer, a JLab staff scientist, and one of the lead authors on the paper. "We eagerly await confirmation, or refutation, of the conclusions of our simple model by realistic theoretical calculations."

Meanwhile, Carman adds, the researchers are planning further experiments. "Our group is continuing this exciting research by extending our arguments to test our picture of the dynamics in different reactions."

These results show that we have much still to learn about the basic structure of the vacuum. One hundred years ago the vacuum was thought to consist of an "ether" through which light propagated as waves. Albert Michelson, Edward Morley, Albert Einstein and others disproved this hypothesis and the vacuum became an empty void. Twentieth century quantum field theories have now filled this once-empty space with virtual particles. It’s now obvious that a vacuum is not the cold, empty place it was once thought to be. JLab physicists and researchers are studying the spin of the produced quarks in hopes of understanding the vacuum better, as well as the matter that populates it.


###
by Mac Mestayer in collaboration with Melanie O’Byrne

Linda Ware | EurekAlert!
Further information:
http://www.jlab.org/

More articles from Physics and Astronomy:

nachricht Computer model predicts how fracturing metallic glass releases energy at the atomic level
20.07.2018 | American Institute of Physics

nachricht What happens when we heat the atomic lattice of a magnet all of a sudden?
18.07.2018 | Forschungsverbund Berlin

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Future electronic components to be printed like newspapers

A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.

The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...

Im Focus: First evidence on the source of extragalactic particles

For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.

To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...

Im Focus: Magnetic vortices: Two independent magnetic skyrmion phases discovered in a single material

For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.

Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...

Im Focus: Breaking the bond: To take part or not?

Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.

A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...

Im Focus: New 2D Spectroscopy Methods

Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.

"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Leading experts in Diabetes, Metabolism and Biomedical Engineering discuss Precision Medicine

13.07.2018 | Event News

Conference on Laser Polishing – LaP: Fine Tuning for Surfaces

12.07.2018 | Event News

11th European Wood-based Panel Symposium 2018: Meeting point for the wood-based materials industry

03.07.2018 | Event News

 
Latest News

A smart safe rechargeable zinc ion battery based on sol-gel transition electrolytes

20.07.2018 | Power and Electrical Engineering

Reversing cause and effect is no trouble for quantum computers

20.07.2018 | Information Technology

Princeton-UPenn research team finds physics treasure hidden in a wallpaper pattern

20.07.2018 | Materials Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>