On June 17, an article on the observation of a charged charmoniumlike structure at BESIII was published in Physical Review Letters (Volume

four-quark combinations that may explain theZc(3900) observations.(image by APS/Alan Stonebraker)

110, Issue 25). A paper from Belle Experiment at KEK appeared on the same issue, which signified that the two experiments have more or less simultaneously detected the signature of a new particle, called the Z_c(3900 ).

Since its 2005 discovery by the BaBar experiment at the SLAC National Laboratory in Stanford California, the Y(4260) particle has continued to mystify researchers. Both the BESIII Experiment at the Beijing Electron Positron Collider in China and the Belle experiment at the Japanese High Energy Accelerator Research Organization (KEK) focused on the research of this particle, and found the even more mysterious particle, the Z_c(3900).

The experiments have now produced more than 460 of these strange Z_c(3900) particles, suggesting that they are real phenomena and not simply a statistical fluke in the data. The new exotic particle appears to have an electric charge, and contains at least a charm quark, an anti-charm quark, an up quark, and an anti-down quark for a total of four quarks.

"We haven’t seen anything like that before and for that reason it’s exciting,” commented Eric Swanson, an associate professor at the University of Pittsburgh, While previous experiments have detected hints of such particles, BESIII and Belle’s data are the cleanest and most experimentally solid to date.”

The next step for both collaborations is to produce more new Z_c(3900) particles and watch how they decay, which should give some clues as to their properties, for example, whether it is a molecule of two mesons or a tetraquark state or other possibilities suggested by the theorists But in any case, the Z_c(3900) is something extremely interesting for a deeper understanding of the matters in the universe.

the data bump from BESIII and Belle (images from physics review letter)

Sources from:

BESIII paper: http://prl.aps.org/abstract/PRL/v110/i25/e252001

Belle paper: http://prl.aps.org/abstract/PRL/v110/i25/e252002

BESIII news: http://english.ihep.cas.cn/prs/ns/201303/t20130326_100230.html

Eric Swanson’s article: http://physics.aps.org/articles/v6/69

News on Wired Magazine: http://www.wired.com/wiredscience/2013/06/four-quark-particle/

Nature: http://www.nature.com/news/quark-quartet-opens-fresh-vista-on-matter-1.13225

Live Science: http://www.livescience.com/37546-new-particle-four-quarks.html

PHYS.ORG: http://phys.org/news/2013-06-collider-teams-evidence-particle-z3900.html