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叙述了J/ψ粒子是由粲夸克和反粲夸克组成的束缚态的实验证明的历史过程,以及发现J/ψ家族,一系列粲介子和粲重子的实验.人们可以从中获得有益的启示. 相似文献
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《物理》编辑部:《物理》2004年第11期第826—831页《J/ψ粒子是由粲夸克和反粲夸克组成的束缚态的实验证明》一文(以下简称《J/ψ粒子》文)中存在多处错误及不够准确的地方,其中与文章主题直接相关的一些内容,即涉及J/ψ粒子家族3个成员——ηc(2S),hc(1P)及ηc(1S)态发现的叙述,更是与实际情况严重不符,需即予更正并及时提请读者注意。 相似文献
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粲重子是含有粲夸克的一类重子。粲重子存在很丰富的激发态,粲重子谱的研究对理解轻夸克在含重夸克系统中的动力学行为,以及检验重夸克对称性和轻夸克手征对称性具有重要意义。Λc+是质量最轻的粲重子,它是由一个粲夸克、一个上夸克和一个下夸克构成的同位旋单态。最近,日本的Belle实验利用在Υ(4S)中心质量采集的772×106对■介子样本,对■衰变过程进行了研究,并在Σc(2455)0,++π±的不变质量谱上发现了一个新的共振结构。在考虑系统误差后,该共振结构最保守的信号显著性为4.2倍标准偏差。这意味着,该结构的形成源于统计涨落和各种系统误差的概率不足0.002%。Belle实验测得这个新结构的质量为(2913.8±5.6±3.8) MeV/c2,宽度为(51.8±20.0±18.8) MeV。虽然这个新结构的性质目前还不完全清楚,但它很符合新的Λc激发态的性质,暂时被命名为Λc 相似文献
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本文给出了级联衰变过程e++e-→J/ψ→V+X,X→P1+Y,Y→P2+P3(V代表矢量介子,Pi代表赝标介子)的角分布螺旋度形式,为通过J/ψ三级二体强衰变过程对中间态X粒子进行自旋-宇称分析提供理论公式. 相似文献
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本文用推广的矩分析方法对J/ψ的强衰变过程J/ψ→V_1+X,X→V_2+V_3,V_2、V_3→2P或3P(其中V_i代表有质量的矢量粒子,P代表赝标介子)进行了讨论.对于具有不同自旋和宇称的中间态X,给出了相应的矩的表达式.在非相对论情况下,计算了过程X→V_3+V_3的螺旋度振幅值.通过比较部分矩的理论值和实验值,可以确定中间态粒子X的自旋、宇称和所处的分波态. 相似文献
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SHEN Cheng-Ping 《中国物理C(英文版)》2010,34(6):615-620
In this paper, I review recent progress in the study of the XYZ particles at Belle. I only focus on studies with charmonium and one or more light mesons in the final states. This covers the X(3872), X(3915),Y(4140), X(4350), and the charged Z states. 相似文献
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A chiral quark model is applied to calculate the spectra of pseudoscalar mesons η and η . By analyzing the obtained spectra, we find that the mesons η (2 1 S 0 ), η(4 1 S 0 ), η (3 1 S 0 ) and η (4 1 S 0 ) are the possible candidates of η(1760), X(1835), X(2120) and X(2370). The strong decay widths of these pseudoscalars to all the possible two-body decay channels are calculated within the framework of the 3 P 0 model. Although the total width of η (21S0 ) is compatible with the BES Collaboration’s experimental value for η(1760), the partial decay width to ωω is too small, which is not consistent with the BES result. If X(1835) is interpreted as η(4 1 S 0 ), the total decay width is compatible with the experimental data, and the main decay modes will be πa 0 (980) and πa 0 (1450), which needs to be checked experimentally. The assignment of X(2120) and X(2370) to η (31S0 ) and η (41S0 ) is disfavored in the present calculation because of the incompatibility of the decay widths. 相似文献
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Jaruwan Siritapetawee Wanwisa Pattanasiriwisawa Unchalee Sirithepthawee 《Journal of synchrotron radiation》2010,17(2):268-272
The trace elements of scalp hair samples from ≥60‐year‐old dementia patients and normal persons have been studied by X‐ray absorption near‐edge spectroscopy (XANES) in fluorescent mode and wavelength‐dispersive X‐ray fluorescence spectrometry. Comparisons of hair trace element levels of age‐matched dementia patients and normal persons revealed significantly elevated amounts of calcium, chlorine and phosphorus in dementia patients relative to normal persons. The results of XANES measurements identify the chemical forms of deposited calcium and phosphorus in the hair samples of both dementia patients and normal persons to be calcium chloride (CaCl2) and phosphate (PO43?), respectively. The amount of sulfur in hairs of dementia patients was found to be not significantly different from that in normal persons. The sulfur K‐edge XANES spectra, however, show significantly higher accumulations of sulfur in the sulfate (SO42?) form in hairs of Alzheimer's disease and Parkinson's disease dementia patients. This study presents the possible roles of calcium, chlorine, phosphorus and sulfur in the etiology of dementia in elderly patients. 相似文献
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A. R. Sandy S. Narayanan M. Sprung J.‐D. Su K. Evans‐Lutterodt A. F. Isakovic A. Stein 《Journal of synchrotron radiation》2010,17(3):314-320
Moderate‐demagnification higher‐order silicon kinoform focusing lenses have been fabricated to facilitate small‐angle X‐ray photon correlation spectroscopy (XPCS) experiments. The geometric properties of such lenses, their focusing performance and their applicability for XPCS measurements are described. It is concluded that one‐dimensional vertical X‐ray focusing via silicon kinoform lenses significantly increases the usable coherent flux from third‐generation storage‐ring light sources for small‐angle XPCS experiments. 相似文献
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采用固相反应法, 制备了钙钛矿结构氧化物LaFe1-xCrxO3较宽范围内(x=0.0—0.7)的系列单相样品, 并测量了各样品的X射线衍射谱(XRD)和扩展X射线吸收精细结构(EXAFS)谱. 通过对XRD的分析样品均为钙钛矿结构正交相, 同时晶格常数随着掺杂量x的增加而减小. 通过对EXAFS的分析和研究得到在LaFe1-xCrxO3氧化物中Fe-O键长和Fe-La键长随掺杂浓度x的变化, 发现Fe-La键长发生比较大的变化, 说明La在体系掺杂中对结构的稳定起到重要作用. 相似文献
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垂直腔面发射激光器的结构生长及特性研究 总被引:1,自引:1,他引:0
在偏〈111〉A 2°的GaAs (100) 衬底上生长了Al0.9Ga0.1As /Al0.2Ga0.8As周期结构的垂直腔面发射激光器(VCSEL)外延片P 型DBR的周期数为24.5对,N型DBR的周期数为34.5对.用光荧光 (PL) 谱、扫描电子显微镜 (SEM)和X射线双晶衍射 (XRD) 方法对VCSEL的光学特性和结构特性进行了分析室温量子阱材料的PL谱峰值波长为837.0 nm,半高宽达到28.9 nm在X射线双晶衍射回摆曲线中,除了“0”级衍射峰外,还观察到一级和二级卫星峰.“0”级双晶衍射峰的半高宽为12.56弧秒(″),衬底GaAs的衍射峰半高宽为11.79″.“0”级衍射峰半高宽与衬底GaAs的衍射峰半高宽比较接近,表明晶格具有很高的完整性.实验结果表明腔模波长为837.2 nm,腔模波长与PL谱峰值波长相匹配. 相似文献
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In this article, we test the nature of X(3872), which is assumed to be a P-wave [cq]-scalar-diquark [cq]-axial-vector-antidiquark tetraquark state with JP=2-. The interpolating current representing the JP=2- state is proposed. Technically, contributions of the operators up to dimension six are included in the operator product expansion. The mass obtained for such state is m2-=(4.38? 0.15) GeV. We conclude that it is impossible to describe the X(3872) structure as JP=2- tetraquark state. 相似文献
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