Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Physicists in Japan and US find new form of matter


Analysis of data from Jefferson Lab’s CEBAF Large Acceptance Spectrometer supports the pentaquark discovery recently announced by the SPring-8 physics lab in Japan.

Physics Lab in Japan reports evidence for the Pentaquark; Jefferson Lab data supports discovery

A Five-quark state has been discovered, first reported by a group of physicists working at the SPring-8 physics lab in Japan. All confirmed particles known previously have been either combinations of three quarks (baryons, such as protons or neutrons) or two quarks (mesons such as pions or kaons). Although not forbidden by the standard model of particle physics, other configurations of quarks had not been found till now. The "pentaquark" particle, with a mass just above 1.5 GeV, was discovered in the following way. At the Spring-8 facility a laser beam is scattered from a beam of 8-GeV electrons circulating in a synchrotron racetrack. These scattered photons constitute a beam of powerful gamma rays, which were scattered from a fixed target consisting of carbon-12 atoms. The reaction being sought was one in which a gamma and a neutron inside a carbon nucleus collided, leaving a neutron, a K+ meson, and a K- meson in the final state. Efficient detectors downstream of the collision area looked for the evidence of the existence of various combinations of particles, including a short-lived state in which the K+ and the neutron had coalesced. In this case the amalgamated particle, or resonance, would have consisted of the three quarks from the neutron (two "down" quarks and one "up" quark) and the two quarks from the K+ (an up quark and a strange antiquark). The evidence for this collection of five quarks would be an excess of events (a peak) on a plot of "missing" masses deduced from K- particles seen in the experiment (

The Laser-Electron Photon Facility (LEPS) at the SPring-8 machine ( ) is reporting exactly this sort of excess at a mass of 1540 MeV with an uncertainty of 10 MeV. The statistical certainty that this peak is not just a fluctuation in the natural number of background events, and that the excess number of events is indicative of a real particle, is quoted as being 4.6 standard deviations above the background. This, according to most particle physicists, is highly suggestive of discovery. (Nakano et al., Physical Review Letters, upcoming article, probably 11 July 2003; text at; contact Takashi Nakano,

Confirmation of this discovery comes quickly. A team of physicists in the US, led by Ken Hicks of Ohio University (, 740-593-1981) working in the CLAS collaboration at the Dept. of Energy’s Thomas Jefferson National Accelerator Facility, has also found evidence for the pentaquark. A photon beam (each photon being created by smashing the Jefferson Lab electron beam into a target and then measuring the energy of the scattered electron in order to determine the energy of the outgoing gamma) was directed onto a nuclear target. The photon collides with a deuteron target and the neutron-kaon (nK+) final state is studied in the CLAS detector ( ). The TJNAF result was announced at the Conference on the Intersections of Nuclear and Particle Physics ( ) held on May 19-24, 2003, at New York City. Stepan Stepanyan (, 757-269-7196) reported at this meeting that the mass measured for the pentaquark, 1.543 GeV (with an uncertainty of 5 MeV), is very close to the LEPS value. The statistical basis of the CLAS measurement is an impressive 5.4 standard deviations. (This result is about to be submitted to Physical Review Letters.) These results, together with the previous results from SPring-8, now provide firmer evidence for the existence of the pentaquark. The HERMES experiment at the DESY lab in Germany is also pursuing the pentaquark particle.

The discovery of a 5-quark state should be of compelling interest to particle physicists, and this might be only the first of a family of such states. Not only that but a new classification of matter, like a new limb in the family tree of strongly interacting particles: first there were baryons and mesons, now there are also pentaquarks. According to Ken Hicks, a member of both SPring-8 and Jefferson Lab experiments, this pentaquark can be considered as a baryon. Unlike all other known baryons, though, the pentaquark would have a strangeness value of S=+1, meaning that the baryon contains an anti-strange quark. Past searches for this state have all been inconclusive. Hicks attributes the new discovery to better beams, more efficient detectors, and more potent computing analysis power.

Linda Ware | EurekAlert!
Further information:

More articles from Physics and Astronomy:

nachricht A new path for electron optics in solid-state systems
15.07.2020 | ETH Zurich Department of Physics

nachricht Black phosphorus-based van der Waals heterostructures for mid-infrared light-emission applications
13.07.2020 | Light Publishing Center, Changchun Institute of Optics, Fine Mechanics And Physics, Chinese Academy

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: A new path for electron optics in solid-state systems

A novel mechanism for electron optics in two-dimensional solid-state systems opens up a route to engineering quantum-optical phenomena in a variety of materials

Electrons can interfere in the same manner as water, acoustical or light waves do. When exploited in solid-state materials, such effects promise novel...

Im Focus: Electron cryo-microscopy: Using inexpensive technology to produce high-resolution images

Biochemists at Martin Luther University Halle-Wittenberg (MLU) have used a standard electron cryo-microscope to achieve surprisingly good images that are on par with those taken by far more sophisticated equipment. They have succeeded in determining the structure of ferritin almost at the atomic level. Their results were published in the journal "PLOS ONE".

Electron cryo-microscopy has become increasingly important in recent years, especially in shedding light on protein structures. The developers of the new...

Im Focus: The spin state story: Observation of the quantum spin liquid state in novel material

New insight into the spin behavior in an exotic state of matter puts us closer to next-generation spintronic devices

Aside from the deep understanding of the natural world that quantum physics theory offers, scientists worldwide are working tirelessly to bring forth a...

Im Focus: Excitation of robust materials

Kiel physics team observed extremely fast electronic changes in real time in a special material class

In physics, they are currently the subject of intensive research; in electronics, they could enable completely new functions. So-called topological materials...

Im Focus: Electrons in the fast lane

Solar cells based on perovskite compounds could soon make electricity generation from sunlight even more efficient and cheaper. The laboratory efficiency of these perovskite solar cells already exceeds that of the well-known silicon solar cells. An international team led by Stefan Weber from the Max Planck Institute for Polymer Research (MPI-P) in Mainz has found microscopic structures in perovskite crystals that can guide the charge transport in the solar cell. Clever alignment of these "electron highways" could make perovskite solar cells even more powerful.

Solar cells convert sunlight into electricity. During this process, the electrons of the material inside the cell absorb the energy of the light....

All Focus news of the innovation-report >>>



Industry & Economy
Event News

Contact Tracing Apps against COVID-19: German National Academy Leopoldina hosts international virtual panel discussion

07.07.2020 | Event News

International conference QuApps shows status quo of quantum technology

02.07.2020 | Event News

Dresden Nexus Conference 2020: Same Time, Virtual Format, Registration Opened

19.05.2020 | Event News

Latest News

When Concrete learns to pre-stress itself

15.07.2020 | Architecture and Construction

New lithium battery charges faster, reduces risk of device explosions

15.07.2020 | Power and Electrical Engineering

A new path for electron optics in solid-state systems

15.07.2020 | Physics and Astronomy

Science & Research
Overview of more VideoLinks >>>