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 Study offers new theoretical approach to describing non-equilibrium phase transitions
27.04.2017 | DOE/Argonne National Laboratory

nachricht SwRI-led team discovers lull in Mars' giant impact history
26.04.2017 | Southwest Research Institute

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: Making lightweight construction suitable for series production

More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.

Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...

Im Focus: Wonder material? Novel nanotube structure strengthens thin films for flexible electronics

Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.

"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Fighting drug resistant tuberculosis – InfectoGnostics meets MYCO-NET² partners in Peru

28.04.2017 | Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

 
Latest News

Wireless power can drive tiny electronic devices in the GI tract

28.04.2017 | Medical Engineering

Ice cave in Transylvania yields window into region's past

28.04.2017 | Earth Sciences

Nose2Brain – Better Therapy for Multiple Sclerosis

28.04.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>