Hadrons are the realization and consequence of QCD in our world. Hadrons, we are able to access experimentally have been limited only to a very narrow apperance although QCD promises an existence of much broader, rich and non-trivial phenomena which our current picture of the world would not reconcile.
As an example, since QCD was established in 1970’s only two kinds of hadrons are known, namely meson (a pair of quark-antiquark) and baryon (composition of 3 quarks). Recently experiments seem to have a grasp of new forms of hadrons. There were series of discoveries of new states that do not fit into the picture of conventional hadron. One possible explanation of such states are a hadron composed by 4 quark states. QCD predicts also a particle composite with, or exclusively with gluons. This open a completely new horizon of an existence of matter.
As another example, matter (hadron) changes its property depending on an environmental condition, i.e. temperature and pressure. This is just like a physical chemistry matter (e.g. water) changed its property from ice (solid state) to water (liquid) to vapour (gas). Our knowledge of the QCD matter is limited to a single point, vacuum, however, a rich and complex phase transitions and phenomena are left over to be explored.
Such experimental exploratory can be enabled with large scale, versatile, wide solid angle detector facilities, e.g. Belle experiment at KEK, Japan and P̅ANDA experiment at FAIR, Germany. These two experiments take distinctly different approaches in order to produce those yet unrevealed hadrons in the laboratory, leptonic e+e– collision and hadronic p̅p collision for Belle and P̅ANDA, respectively. Both approaches have superiority over the other, complementing each other the study of QCD.
The BELLE Experiment
The BELLE experiment was built primarily to study the CP violation in B meson system. The e+e– collider machine was tuned at Y(4S) resonance that falls into a dominant decay channel of B meson pair production. In order to obtain a firm evidence of the tiny CP violation, the BELLE experiment had been running with the world highest luminosity for nearly 10 years, accumulating an enormous statistics of high quality data. [Read more...]
The PANDA Experiment
The PANDA Experiment is one of the large scale projects at FAIR. It will study antiproton annihilations on nucleons and nuclei in the energy range of strange and charmed hadrons. A synchrotron and storage ring (HESR) will provide an antiproton beam with very small momentum spread (2x10-5) or high luminosity (2x1032 cm-2s-1). The commissioning of the experiment at FAIR is planned to start in 2020. [Read more...]