The Beijing Spectrometer III(BESIII)International Cooperation Group announced on the 19th that a new resonant structure has been discovered in the recently collected data,and it has been temporarily named Zc(3900).The particles in the charm energy region generally contain charm quarks and anti charm quarks,known as charmonium,which are neutral and uncharged.The newly discovered Zc(3900)contains charm quarks and anti charm quarks,and has the same or opposite charge as the electron.This suggests that it contains at least four quarks,which may be a peculiar hadron that scientists have been searching for for a long time.
Shen Xiaoyan,spokesperson for the BESIII Experimental International Cooperation Group and deputy director of the Experimental Physics Center at the Institute of High Energy,Chinese Academy of Sciences,said,"The search for new hadron states that go beyond traditional quark models has always been one of the most important physical goals of the Beijing Spectrometer experiment.The discovery of charged Zc(3900)is likely to open a door for the search and study of new hadron states."
It is understood that the traditional quark model believes that mesons are composed of one quark and one anti quark,baryons are composed of three quarks or three anti quarks,and mesons and baryons are collectively referred to as hadrons.However,the theory describing strong interactions between quarks does not exclude particles composed in other ways,such as quark gluon hybrid states,hadron molecular states,multi quark states,gluon spheres,etc.The academic search for these peculiar hadrons has never stopped,but the current evidence is not sufficient to confirm their existence.Many international experiments have extensively studied the hadron spectrum and discovered a series of new resonance structures,but due to the lack of data and theoretical limitations,the properties of these particles cannot be determined yet.
It is reported that the Beijing Electron Positron Collider/Beijing Spectrometer was modified in 2009 to measure the decay products after electron positron collisions and reconstruct the collision process.The discovered Zc(3900)has a slightly larger mass than a helium atom,a shorter lifespan,and decays into a charged particle and a J/within 10-23 seconds?Mane particles.This property is completely different from ordinary meson states.Industry experts believe that although its properties such as spin and parity quantum numbers,other decay and generation modes are still unknown,this new discovery provides strong evidence for the existence of peculiar hadron states,which is of great significance for quantitatively understanding how hadrons are composed of quarks and testing the theory of strong interactions.
"It is believed that with the accumulation of more data,we will have a deeper understanding of the properties of Zc(3900)and other new particles discovered internationally in recent years,"said Wang Yifang,director of the Institute of High Energy Physics of the Chinese Academy of Sciences.(Reporter Zhang Qiaoling)
