Belle实验上发现新的矢量粒子

Belle实验在Υ(4S)共振态及其附近采集了大量数据,利用初态辐射(ISR)的方法,测量了e+e-→π+π-J/ψ,π+π-ψ(2S)和K+K-J/ψ等过程从阈值到5.5 GeV间的产生截面.证实了BaBar合作组发现的Y(4260)和Y(4360)的存在,并更新了其共振参数,同时发现了Y(4008)和Y(4660)两个共振结构.以上观测与已知的粲偶素粒子性质不同,可能是新的粲偶素态,也可能是粲偶素混杂态,或者由其他未知的动力学原因造成.     

Belle实验上发现新的矢量粒子

Belle实验在Y(4s)共振态及其附近采集了大量数据,利用初态辐射(ISR)的方法,测量了e e-→π π-J/ψ,π π-ψ(2S)和K K-J/ψ等过程从阈值到5.5 GeV间的产生截面.证实了BaBar合作组发现的Y(4260)和Y(4360)的存在,并更新了其共振参数,同时发现了Y(4008)和Y(4660)两个共振结构.以上观测与已知的粲偶素粒子性质不同,可能是新的粲偶素态,也可能是粲偶素混杂态,或者由其他未知的动力学原因造成.     

BESⅢ实验首次观测到Y(4260)→γX(3872)辐射跃迁

<正>随着我国北京正负电子对撞机(BEPCII)上的北京谱仪(BESIII)实验和日本高能加速器研究机构(KEK)的Belle实验发现带电奇特强子态ZC(3900)[1],研究奇特态粒子成为粒子物理学研究领域中当前最热门的课题之一。究竟什么是奇特态粒子呢?这还得追溯到基本粒子的结构。     

BES Ⅲ实验发现奇特强子态Zc(3900)

2013 年3 月26 日,北京谱仪Ⅲ(BES Ⅲ)实验国际合作组宣布,在最近采集的一批实验数据中,发现了一个新的共振态结构,暂时命名为Z_c(3900)。     

在BEPCⅡ/BESⅢ上寻找η′c和1P1的Monte Carlo研究

使用SimBes(探测器模拟软件)和UGNT(物理事例产生器)模拟了在即将建造的BEPCⅡ/BESⅢ上寻找η′c和1P1的过程. 初步结论是如果收集到3×109ψ(2S)事例,就有能力寻找这两个粒子,而且,寻找η′c比寻找1P1需要更少的ψ(2S)事例.     

强电场对夸克胶子等离子体中粲夸克偶素演化的影响(英文)

在极端相对论重离子碰撞中,高速运动的重离子会产生很强的电场。在碰撞的早期电场强度大小在eE~m_π2的量级。在夸克胶子等离子体中,强电场将会对粲夸克偶素的演化产生巨大的影响。我们用含时薛定谔方程计算夸克胶子等离子体中由高速运动电荷所产生强电场对重夸克偶素演化的影响。此电场可以导致不同角动量态之间的跃迁。为了研究此效应,比较了有电场和无电场情况下J/ψ、ψ'以及χ_c的产额。计算结果表明,在碰撞早期电场会导致J/ψ解离;同时,χ_c也由电场导致的J/ψ的跃迁而产生。     

Belle实验ϒ(5S)数据中新类底偶素态的寻找

Belle实验组利用在ϒ (5S)共振峰上采集的大数据样本,对e⁺e^－→π⁺π^－ϒ (nS)和π⁺π^－h_b (mP) (n=1,2,3,m=1,2)过程进行了研究,在π^±ϒ (nS)和π^±h_b(mP)的系统中,同时观测到了两个新的带电类底偶素结构——Z_b(10610)和Z_b(10650)。它们衰变到底偶素末态,同时还带有电荷,所以它们的组成成份中至少含有4个夸克。最近,对e⁺e^－→π⁺π^－π⁰ γ ϒ (1S)过程也进行了研究,在ωϒ (1S)系统中对类X(3872)的底偶素态X_b进行了寻找。     

Belle实验?(5S)数据中新类底偶素态的寻找

Belle实验组利用在?(5S)共振峰上采集的大数据样本,对e+e－→π+π－?(nS)和π+π－hb (mP)(n=1,2,3,m=1,2)过程进行了研究,在π±?(nS)和π±hb(mP)的系统中,同时观测到了两个新的带电类底偶素结构——Zb(10610)和Zb(10650)。它们衰变到底偶素末态,同时还带有电荷,所以它们的组成成份中至少含有4个夸克。最近,对e+e－→π+π－π0γ?(1S)过程也进行了研究,在ω?(1S)系统中对类X(3872)的底偶素态Xb进行了寻找。     

胶子遮蔽和末态作用对p—A碰撞中粲偶素和b夸克偶素产额压低的贡献

本文用胶子结构函数的遮蔽效应和末态作用分析了在p-A碰撞中粲偶素和b夸克偶素产额压低的实验数据,较好地描述了粲偶素和b夸克偶素产额的压低与A和X2的关系.     

胶子遮蔽和末态作用对p—A碰撞中粲偶素和b夸克偶素产额压低的贡献

本文用胶子结构函数的遮蔽效应和末态作用分析了在ｐ－Ａ碰撞中粲偶素和ｂ夸克偶素产额压低的实验数据，较好地描述了粲偶素和ｂ夸克偶素产额的压低与Ａ和Ｘ２的关系．     

3π强子物理和实验

在强子物理研究中,3π产生的理论和实验有非常重要的意义,是目前世界上很多大型实验设备的重要研究对象。3π强子物理包含丰富的物理内容,可以作为探索低能区强相互作用的有力工具。同时,3π产生过程是寻找奇特轻介子态的主要途径之一。另外,通过研究3π产生反应道还可以寻找“失踪”共振态和重子激发态之间的级联衰变。介绍了目前国际各大高能物理实验室的3π产生过程的实验、理论研究以及分波分析技术现状,重点介绍了美国杰弗逊国家实验室（Jefferson Lab,简称JLab）的CLAS（CEBAF Large Acceptance Spectrometer）实验上的3π反应过程。最后,指出了3π强子物理研究的意义和未来的研究方向。Three pion productions off nucleon are of significance in the research of hadron physics. Meanwhile it is the subject of many big experimental apparatus in the world. Due to the variety of three pion productions, it can be applied as an effective tool to study QCD in low energy region. Three pion productions is one of the main reactions in searching light exotic meson state. Moreover, it is possible to find out the "missing" baryon resonance and the cascaded decay process between baryon excited states. We introduce present experiments and theories of three pion productions as well as the partial wave analysis technique. The emphasis is on the CLAS (CEBAF Large Acceptance Spectrometer) experiment at JLab (Jefferson Lab). In the end, we point out the significance of studying the three-pion hadron physics at JLab.     

发现ZC（3900）--一个带电类粲偶素共振结构*

北京谱仪(BESⅢ)实验和Belle实验利用两种不同的方法对e+e-→p+p-J/y过程进行了研究。在p±J/y系统中,同时观测到了一个新的带电类粲偶素结构--ZC(3900)。ZC(3900)耦合到粲偶素末态,因此其内部夸克组分应该含有正反粲夸克;同时它还带有电荷,故不可能仅由正反粲夸克组成。ZC(3900)共振态中最少含有4个夸克,极有可能是一个奇特态强子。     

Search for exotic state 1-+ π1(1400) at BESⅢ

The J/ψ hadronic decays provide good laboratory to search for the hybrid states with exotic quantum numbers. A full Partial Wave Analysis (PWA) is performed to the generated Monte Carlo J/ψ→ pηπ data, based on the design of BESⅢ detector, to study the sensitivity of searching for a possible exotic state at BESⅢ.     

北京谱仪BESIII精确测量Y(4260)粒子

利用北京谱仪BESIII实验采集的约9fb^－1数据样本,BESIII测量了e^＋e^－→π^＋π^－J/ψ过程的产生截面,并对在该过程中观测到的Y(4260)粒子的质量和宽度做了目前世界上最精确的测量。BESIII的测量给出Y(4260)粒子的质量在4.22 GeV/c²左右,比之前的测量偏低;宽度约44 MeV,比之前的测量窄很多。相比之前的实验,BESIII对Y(4260)粒子参数的精确测量给解释该粒子的理论模型提供了更强的约束。另外,BESIII实验在4.32 GeV/c²附近还观测到一个新粒子信号,信号显著性为7.6σ。新粒子的质量和宽度和之前观测到的Y(4360)粒子的质量和宽度在误差范围内吻合,有可能是同一个粒子。     

Decay properties of the X(3872) through the Fierz rearrangement

We systematically construct all the tetraquark currents of J^PC = 1⁺⁺ with the quark configurations $[{cq}][\bar{c}\bar{q}]$, $[\bar{c}q][\bar{q}c]$, and $[\bar{c}c][\bar{q}q]$ (q = u/d). Their relations are derived using the Fierz rearrangement of the Dirac and color indices, through which we study decay properties of the X(3872) under both the compact tetraquark and hadronic molecule interpretations. We conduct a search for the X(3872) → χ_c0π, η_cππ, and χ_c1ππ decay processes in particle experiments.     

Vector hidden-bottom tetraquark candidate: Y(10750)

In this article,we take the scalar diquark and antidiquark operators as the basic constituents,and construct the Cγ_5■γ_5C type tetraquark current to study Y(10750) with the QCD sum rules.The predicted mass M_Y=10.75±0.10 GeV and width Γ_Y=33.60_(-9.45)~(+16.64) MeV support the assignment of Y(10750) as the diquark-antidiquark type vector hidden-bottom tetraquark state,with a relative P-wave between the diquark and antidiquark constituents.     

New Crystalline Lasers on the Base of Monoclinic KR(W04)2:Ln3+ Tungstates (R=Y and Ln)

Monoclinic KY(WO₄)₂:Pr₃₊, Tm₃₊:KY(WO₄)₂:Er₃₊, Yb₃₊ single crystals are grown by low-gradient Czochralski technique. Stimulated emission at 1.0223μm wavelength in the new lasing ¹D₂→³F₃ channel of Pr³⁺ ions in KY(WO₄)₂ at room temperature under Xe-flashlamp pumping is excited. Full sets of Stark-level energies for Pr₃₊ ions in KY(WO₄)2 and KGd(WO₄)₂ crystals at 77 K are determined. 4f²-4f² intensity-transitions for the KY(WO₄)₂:Pr³⁺ are analyzed preliminarily. All observed at present and earlier one-micron Pr³⁺-ion, induced transitions in the ¹D₂→³F₃ and ¹D₂→³F₄ channels are identified. In yttrium and gadolinium sensitized-tungstates a two-micron (³H₄→³H₆) low-threshold generation of Tm³⁺ ions at cryogenic temperatures is achieved.All authors cooperate with the Joint Open Laboratory for Laser Crystals and Precise Laser Systems at the Institute of Crystallography and Institute of Laser Physics, Russian Academy of Sciences.     

D* D1 and D D'*(2600) interactions and the charged charmonium-like state Z(4430)

The D^*D₁(2420) and DD'^*(2600) interactions are studied in a one-boson-exchange model. Isovector bound state solutions with spin parity J^P=1⁺ are found from the D^*D₁(2420) interaction, which may be related to the observed charged charmonium-like state Z(4430). There is no bound state solution found from the DD'^*(2600) interaction.     

Existence and transition properties of the three-deuteron muonic molecule (3d,2e -,μ-)

We calculated the energy and the size of the three-deuteron muonic molecule (3d,2e ^-,μ^-) = D₃μ. It turns out that this system possesses two equilibrium positions, one at distances typical for muonic molecules, the second one at the usual molecular size. We show, moreover, that the fusion probability of the three deuterons is considerably enhanced due to the existence of a ⁶Li^* threshold resonance. Our estimates indicate that this probability is considerably higher than the decay rate of the competing Auger transition. This revised version was published online in August 2006 with corrections to the Cover Date.     

Electronic structure and magnetism of R(Fe,Si)12 (R = Y, Nd)

The newly developed full-potential linearized augmented plane wave (LAPW) and local orbitals (lo) based on standard APW methods are briefly introduced, and the structure and magnetic properties of R(Fe, Si)12 compounds (R = Y, Nd) are calculated using the method. The distribution of Si at different sites is analyzed based on total energy of one crystal unit with structure having been optimized. The characters of magnetic moments, total density of states (TDOS) and partial density of states (PDOS) for different crystal sites Si occupies are obtained and analyzed. The results show that the total magnetic moments of RFe10Si2 (R = Y, Nd) are larger than those of RFe10M2 (M = Ti, V, Cr, Mn, Mo and W) and the hybridization mechanism is seen as follows. Si(8j) reduce the magnetic moments of Fe at three sites, however, Si(8f) mainly reduce the magnetic moments of Fe(8i) and Fe(8j) atoms. The Curie temperature is markedly enhanced by the introduction of Si atoms according to spin fluctuation of DOS at Fermi level.