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The study of non-singular dibaryon

Author: ZhuXinMei
Tutor: PingJiaLun
School: Nanjing Normal University
Course: Theoretical Physics
Keywords: QDCSM dibaryon state deuteron components of △△ decay width of △△→NN
CLC: O572
Type: Master's thesis
Year: 2004
Downloads: 20
Quote: 0
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Abstract


Dibaryon search is an important subject. It is a new structure of matter. On the other side, the freedom of the system will be enlarged accompanying with the increase of the particle number. For example, we have new color structure here. The investigation of the dibaryon can also make further test of the quark models which have successfully described the properties of the hadrons. Therefore, The study of dibaryon will supply a wider realm to understand and test QCD. Several dibaryon states such as d , d* N di- and so on have been predicted by some models since the first prediction of H dibaryon by Jaffe in 1977. Unfortunately, there is no any convincing evidence in experiments to demonstrate the existence of the dibaryon. The dibaryon states without strangeness: NN, N△ and △△ are much easier to be realized in experiments. In general, because of the more strong attraction, the system of AA is inclined to form the resonant state easier than the other. So discussing the resonant states of AA is our main goal in this paper. Recently, in some reactions such as the ant iproton-duteron annihilation and the elastic proton-deuteron backward scattering, those non-nucleonic components in the deuteron could be indirectly observed, which invoked more people to take further study on the detail property of the deuteron 梩he only dibaryon state in nature. Consequently, analyzing the AA components in the deuteron has also been done in this work.Any model which is to be applied to study the dibaryon state should firstly describe the baryon well. The effective theory based on the exchange of bosons at the baryon level can explain the baryon-baryon scattering data well. However, it is not easy to extend these theories to the dibaryon state because they take the baryon and meson as effective degrees of freedom. So many people turn to study the problem from the more essential degrees of freedom such as quark gluon Goldstone boson and so on. Quantum Chromodynamics (QCD) is generally accepted as the fundamental theory of the strong interaction, its effective degrees of freedom are quarks and gluons. High energy processes are calculable using perturbative method due to the asymptotic freedom property of QCD. However, owing to the infrared confinement, low and middle energy strong interaction systems can notbe resolved directly according to QCD. At present and even in the future, the QCD-inspired model will be a useful tool to explore the secret of strong interaction systems. There are a lot of quark models now, constituent quark model, bag model, soliton model etc. Under the framework of constituent quark model, according to the effective degrees of freedom used, we have the Glashow-Isgur model , the spontaneous chiral symmetry breaking model, the hybrid model and so on.All of these models are successful to describe the properties of the mesons and baryons. But there will be more or less flaws when these models are extended to explore the interaction of hadrons. For example, Glashow-Isgur model can not give the intermediate interaction of nuclear force. So it is necessary to extend those models. In 90s of the 20th century Professor Wang Fang and his group developed a new model梣uark delocal ization color screening model (QDCSM) based on the Glashow-Isgur model. This model not only can successfully depict the properties of baryons, but also can give the intermediate attraction of nuclear force. Moreover, QDCSM is a "parameter-free" model in some sense, so the model is more predictive. QDCSM has been applied to the study of baryon-baryon scattering, systematic search of dibaryon candidates and so on. In this work, we investigate the AA systems in detail by using the extended QDCSM (adding pion meson exchange with short range cutoff). First, we calculated the AA components in the deuteron. Then, for some channels of AA which have the deeper attraction, we calculated the energy of the system and the decay width of the system to explore the probability of looking AA dibaryons in experiments. On the one hand, we wish to make furthe

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