在势模型框架下对Z+（4430）的动力学研究
时间:2019-10-26 19:13 来源:毕业论文 作者:毕业论文 点击:次
| 摘要欧洲核子研究中心的大型强子对撞机 LHCb 宣布观测到一个异乎寻常的状态， 一个看起来由四个夸克组成的奇怪粒子状态。因为它的异乎寻常，研究人员将这个粒子叫做 Z+（4430），这意着它的质量为4430MeV，这几乎是质子质量的四倍。并且它还带着正电荷。 字母 Z 表示他是属于 XYZ 状态的一系列奇怪粒子中的一个。 那么，这种状态究竟奇怪在哪里？传统的夸克模型中有优尔个不同的夸克子， 每一个夸克子都有它的反粒子。所有粒子都由这些夸克子中三个或四个形成束缚态。举个例子，纸质和中子就是由三个夸克形成的。所有由三个夸克形成的状态都叫做重子态。其他如由于更重的粒子衰减形成的介子和和Ｋ介子是由一个夸克和一个反夸克组成的。 这些就形成介子这个类别，直到 2003年，数以百计的的既不是介子也不是重子的粒子被观测到。2007 年，Belle 合作组宣布发现了Z+(4430)。丰富的数据样本使得合作组能够比较明确的观测这个粒子的性能，使得科学家们能够确定 Z+（4430）究竟是什么粒子。理论物理学家们正在试图建构有一个新的模型来描述这些新的状态。究竟这些是新的粒子是四夸克还是由这些夸克子组成的束缚态，亦或是由两个粲介子混合组成（粲介子至少包括一个粲夸克）这些问题还没有得到解决。我们已经研究了在夸克模型中将 Z+（4430）作D*D1分子态。如果计算的出的质量与 D*D1的阈值接近，则可以判别Z+（4430）粒子的可能组成结构。本文的模型预测结果也很好的符合了势模型和 QCD 理论。本文在势模型框架下对 Z+（4430）粒子进行动力学研究。首先介绍了一下目前国际上对 Z+（4430）粒子的研究状况。选取探究 Z+（4430）粒子是否为D*D1分子态进行研究。描绘图像。就最后就计算所得的 Z+(4430)的质量与D*D1的阈值进行比较，分析 Z+（4430）可能组成方式，并给出结论。41410 该论文有图 10幅，表 2个，参考文献 10篇 The dynamical study of Z + (4430) in potential modeAbstractThe LHCb Collaboration at CERN has just confirmed the unambiguous observationof a very exotic state, something that looks strangely like a particle being made of fourquarks. As exotic as it might be, this particle is sternly called Z+(4430) which gives itsmass at 4430 MeV, roughly four times heavier than a proton, and indicates it is has anegative electric charge. The letter Z shows that it belongs to a strange series of particlesthat are referred to as XYZ states. So what’s so special about this state? The conventionaland simple quark model states that there are six different quarks, each quark coming withits antiparticle. All these particles form bound states by either combining two or three ofthem. Protons and neutrons for example are made of three quarks. All states made of threequarks are called baryons. Other particles like pions and kaons, which are often found inthe decays of heavier particles, are made of one quark and one antiquark. These form themesons category. Until 2003, the hundreds of particles observed were classified either asmesons or baryons. 2007，the Belle experiment confirmed Z+（4430）.The data sample isso large that it enabled LHCb to measure some of its properties unambiguously. it allowsphysicists to find out exactly what kind of particle it is. Theorists are hard at work nowtrying to come up with a model to describe these new states. Is this a completely newtetra-quark, a bound state of four quarks, or some strange combination of two charmedmesons (mesons containing at least one charm quark)? The question is still open.We have studied Z+(4430) as a D*D1 molecule from the quark model, if the mass of the meson we calculate is close to the D*D1 threshold. Then we can analysethe possible composition.n this thesis, we focus on the dynamical study of the heavy-flavor meson-meson molecular states in potential model. Firstly, we introduce thecurrent research status of it.Secondly, We choose whether Z+（4430) is a D*D1 molecule state as the object of the study.Finally , we compare the mass we calculated with the D*D1 threshold and analyse the possible composition mode, giving the conclusion. (责任编辑：qin) |