Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Higher Precision Analysis Doesn’t Yield Pentaquark

07.07.2005


New, higher precision data that could only have been gathered at the Department of Energy’s Thomas Jefferson National Accelerator Facility (Jefferson Lab) shows the Theta-plus pentaquark doesn’t appear in another place it was expected. This intriguing finding contradicts evidence previously presented by Jefferson Lab researchers that they had sighted a pentaquark, a particle built of five quarks. Volker Burkert, a Jefferson Lab Experimental Hall Leader, will present this preliminary result in a talk reviewing world pentaquark data at Lepton-Photon, the XXII International Symposium on Lepton-Photon Interactions at High Energy, in Uppsala, Sweden, on Friday, July 1.


Researchers sent photons into deuterium nuclei to try to produce pentaquarks. If pentaquarks had been produced, sensitive detectors would have measured a particular mix of Kaons (K-mesons) and protons; neutrons could have been inferred from the data. The researchers did not detect this reaction. Image credit: JLab



The result comes from a very carefully crafted experiment that was designed to repeat Jefferson Lab’s original pentaquark search with a factor of ten higher statistics. Researchers in Jefferson Lab’s CEBAF Large Acceptance Spectrometer (CLAS) collaboration took data with a high-energy photon beam on a deuterium target March 13 – May 16, 2004. Deuterium is an isotope of hydrogen with one proton and one neutron in its nucleus. An earlier probe of this same region by CLAS revealed a possible signal for a pentaquark with mass 1542 MeV.

The new experiment searched for pentaquarks in this same channel at a level of precision at least 10 times higher, or one order of magnitude better, than the previous published result and found no pentaquarks. “The earlier results on the Theta-plus can not be reproduced in the analysis of the high-statistics run,” Burkert says.


Faced with this result, the collaboration re-analyzed the data from the original experiment, taking into account a new understanding of the background obtained from the recent run and improved statistical analysis software. The re-analysis revealed a much weaker signal for the pentaquark in the original experiment.

“One of the problems with the first pentaquark finding is that we didn’t completely understand the background,” Burkert says, “The statistical significance stated in the earlier result is likely due to a combination of statistical fluctuation with an underestimate of the background. We eliminated that problem with the second, higher-statistics run and a more rigorous analysis.”

The first pentaquark sighting was announced by SPring-8 researchers in the spring of 2003, and the same year, Jefferson Lab, ITEP and ELSA researchers announced that they, too, may have spotted tantalizing hints of the particle in data previously taken in other experiments. Several experiments since then have backed up these early sightings, while others have failed to confirm them. Jefferson Lab researchers are currently in the midst of several dedicated hunts for the pentaquark.

Most ordinary matter is built of quarks. They’re usually found in twos (as particles called mesons) and threes (as particles called baryons, such as protons and neutrons). While the pentaquark’s five-quark configuration is not forbidden by the theory of the strong interaction, finding one would be the first sighting of an exotic baryon.

For more information, or to schedule an interview, contact:
Kandice Carter, kcarter@jlab.org or ph. (757) 269-7263
or Linda Ware, ware@jlab.org or ph. (757) 269-7689

Thomas Jefferson National Accelerator Facility’s (Jefferson Lab’s) basic mission is to provide forefront scientific facilities, opportunities and leadership essential for discovering the fundamental structure of nuclear matter; to partner in industry to apply its advanced technology; and to serve the nation and its communities through education and public outreach. Jefferson Lab, located at 12000 Jefferson Avenue, is a Department of Energy Office of Science research facility managed by the Southeastern Universities Research Association.

Kandice Carter | EurekAlert!
Further information:
http://ww.jlab.org

More articles from Physics and Astronomy:

nachricht Further Improvement of Qubit Lifetime for Quantum Computers
09.12.2016 | Forschungszentrum Jülich

nachricht Electron highway inside crystal
09.12.2016 | Julius-Maximilians-Universität Würzburg

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: Electron highway inside crystal

Physicists of the University of Würzburg have made an astonishing discovery in a specific type of topological insulators. The effect is due to the structure of the materials used. The researchers have now published their work in the journal Science.

Topological insulators are currently the hot topic in physics according to the newspaper Neue Zürcher Zeitung. Only a few weeks ago, their importance was...

Im Focus: Significantly more productivity in USP lasers

In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.

Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...

Im Focus: Shape matters when light meets atom

Mapping the interaction of a single atom with a single photon may inform design of quantum devices

Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

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...

Im Focus: Quantum Particles Form Droplets

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...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

Researchers identify potentially druggable mutant p53 proteins that promote cancer growth

09.12.2016 | Life Sciences

Scientists produce a new roadmap for guiding development & conservation in the Amazon

09.12.2016 | Ecology, The Environment and Conservation

Satellites, airport visibility readings shed light on troops' exposure to air pollution

09.12.2016 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>