对北京谱仪上新观测态的一个理论解释

最近, 北京谱仪在J/ψ的辐射衰变中发现, 在正反质子的阈附近有反常增强, 即可能存在共振态X(1860)和X(1835). 针对这一发现, 提出了新粒子的三胶子胶球态解释方案, 并且应用QCD求和规则计算了此胶球态的质量. 考虑到理论上的不确定因素, 计算结果表明该胶球态的质量峰位于1.9GeV到2.7GeV之间. 事实上, 北京谱仪发现的新共振态的确表现出了一些三胶子态的行为. 结论是, 此新粒子很有可能是重子偶素和胶球态的混合态.     

质子衰变实验进展

按照粒子物理标准模型理论,重子数是绝对守恒的.而大统一理论(GUTs)明确地否定了重子数的对称性,预言质子会衰变成更轻的次粒子.文章论述了质子衰变的物理概念、基本探测条件和主要实验现状,并在探测方法的探讨和探测技术的改进方面融入了一些想法.目前一般认为质子的寿命为τp>1032年左右.质子衰变的探测,对于新理论模型的验证、宇宙学和粒子物理学的发展具有重要意义.     

X(1835): A Possible Baryonium

We point out that the large p(p) coupling of X(1835) and the suppression of the three-body strange final states strongly indicate that X(1835) may be a p(p) baryonium. We also point out that the branching ratio of X(1835) →ηππ should be bigger than that of X(1835) →η′ππ. We suggest BES search X(1835) in the ηππ channel Finally, X(1835)may be used a tetraquark generator if X(1835) is really established as a baryonium state.     

正电子偶素寿命之谜得到解答

电子偶素是由一个电子和一个正电子组成的短寿命类原子体系 .如果其中的电子和正电子的自旋平行 ,称为正电子偶素 ,如反平行则称为仲电子偶素 .由于电子与正电子相互吸引 ,发生湮灭 ,正电子偶素衰变成三个光子 ,仲电子偶素衰变成两个光子 .测量电子偶素的衰变率 ,可以对量子电动力学进行检验 .量子电动力学预言 ,正电子偶素的寿命约为 14 2ns,然而以前的实验测量结果要比这一理论值低 0 .1%以上 ,这就是所谓的正电子偶素寿命之谜 .为说明这种分歧 ,理论家们不得不采用一些奇特的解释 ,比如 ,假设存在轴子、C -odd玻色子、电荷少于千分之一…     

p,在北京谱仪(Ⅱ)中的行为研究

从MonteCalor模拟和北京谱仪 (BESⅡ )所取的实验数据入手 ,分析了p和 p产生次级带电径迹和中性径迹的几率以及好径迹选择条件对这些次级径迹的去除情况、p在探测器中的能量损失和 p的湮没、p和 p在桶部簇射计数器中沉积能量的分布以及 3种不同的粒子鉴别方法的优劣 .给出了BES目前可以正确重建出的p和 p的动量的最小值和利用TOF和dE dx的联合信息鉴别p和 p的优越性 .     

C_2羣和弱相互作用对称性

Cabibbo从几个合理的假定出发,讨论了弱相互作用重子流么正(SU_3)对称性,预言了△S=△Q奇异粒子轻子衰变的分支比,与实验符合得较好。在此基础上,d’Espag-nat进一步考虑了重子流、中间玻色子和弱相互作用拉氏算符的么正对称性,提出了一个值得注意的理论方案,定性地讨论了弱相互作用的主要特点:解释△S≠2和|△I|=1/2非轻子衰变的选择定则;△S=△Q和△S=0轻子衰变的结果估计与Cabibbo的结果相仿(尚未看到详细报导)。     

宇宙中的光子数、重子数、及反重子数

在粒子物理与宇宙学二者的结合上,近年已经取得了颇有意义的进展。重子不对称和重子光子数比的起源可以用大统一理论加以解释。由B、C及CP破坏的相互作用可以说明为什么初始重子对称的宇宙能演化成不对称的。目前观测到的重子光子数比10~(-9)可能是由极早期宇宙中的超重玻色子的衰变产生的,在这种衰变中C及CP是破坏的。尽管衰变解释是吸引入的,但它的具体预言很强地依赖于超重玻色子的质量,以致其数值尚不确定。因此。为了进一步考查衰变模型的合理性,至少还要研究其他的可能有影响的过程。在这个意义下,本文还讨论了宇宙早期中的Higgs相变对重子光子比的影响。     

宇宙中的光子数、重子数、及反重子数

在粒子物理与宇宙学二者的结合上,近年已经取得了颇有意义的进展。重子不对称和重子光子数比的起源可以用大统一理论加以解释。由B、C及CP破坏的相互作用可以说明为什么初始重子对称的宇宙能演化成不对称的。目前观测到的重子光子数比10~(-9)可能是由极早期宇宙中的超重玻色子的衰变产生的,在这种衰变中C及CP是破坏的。尽管衰变解释是吸引入的,但它的具体预言很强地依赖于超重玻色子的质量,以致其数值尚不确定。因此。为了进一步考查衰变模型的合理性,至少还要研究其他的可能有影响的过程。在这个意义下,本文还讨论了宇宙早期中的Higgs相变对重子光子比的影响。     

p,p在北京谱仪(Ⅱ)中的行为研究

从Monte Calor模拟和北京谱仪(BESⅡ)所取的实验数据入手,分析了p和p产生次级带电径迹和中性径迹的几率以及好径迹选择条件对这些次级径迹的去除情况、p在探测器中的能量损失和p的湮没、p和p在桶部簇射计数器中沉积能量的分布以及3种不同的粒子鉴别方法的优劣.给出了BES目前可以正确重建出的p和p的动量的最小值和利用TOF和dE?dx的联合信息鉴别p和p的优越性.     

粲偶素衰变过程中ρπ疑难的研究

详细回顾并广泛评论了粲偶素衰变过程中有关ρπ疑难的各种理论解释和探讨. 在可能的情况下, 将有关的理论预言与相应的实验数据进行了细致的比较. 描述并讨论了三种估算ψ′和J/ψ衰变分支比比值的方法. 针对目前的现状, 指出为了深入理解ρπ疑难以及更进一步了解粲偶素衰变的动力学机制, 需要从理论探究、唯象分析和实验测量多方面进行系统、深入和全面的工作.     

ASE Noise-Reduced Optical Receiver Based on MZI Diversity Scheme

A novel method is proposed that reduces the bit error rate (BER) in an optically amplified system by using a Mach–Zender interferometer coherence manipulation at the receiver. Exact analysis is presented, which shows that the signal-to-noise ratio can be improved by 3 dB. Resulting BER improvements are presented.     

Er0.1La0.9P5O14非晶的双光子上转换发光

本文研究了全浓度ＥｒＬａＰ５Ｏ１４非晶在波长λ为６４９．０ｎｍ脉冲染料激光激发下的上转换发光现象，并对其进行了简要的分析。     

Design of adaptive spatial filter at uniform standard for automatic analysis of digital holographic microscopy

The spatial filtering method is a useful technique for the dynamic and automatic analysis in digital holographic microscopy. It has been shown that the proper selection of the spatial filter would improve the quality of the reconstructed image. However different results would be obtained by employing the spatial filter with different parameter threshold decided at different standard. This paper, according to the histogram analysis of the distribution of the +1 term spectrum of each hologram, gropes for the uniform standard for the decision of the threshold of the adaptive filter. It helps the adaptive spatial filtering method to be more advantageous for the dynamic and automatic analysis.     

Effects of Montmorillonite on the Nonisothermal Crystallization Behavior of the Poly(trimethylene terephthalate)/Polypropylene/Montmorillonite Nanocomposites

Organic montmorillonite (MMT) reinforced poly(trimethylene terephthalate) (PTT)/ polypropylene (PP) nanocomposites were prepared by melt blending. The effects of MMT on the nonisothermal crystallization of the matrix polymers were investigated using differential scanning colorimetry (DSC) and analyzed by the Avrami equation. The DSC results indicated that the effects of MMT on the crystallization processes of the two polymers exhibited great disparity. The PTT's crystallization was accelerated significantly by MMT no matter whether PTT was the continuous phase or not, but the thermal nucleation mode and three-dimensional growth mechanism remained unchanged. However, in the presence of MMT, the PP's crystallization was slightly retarded with PP as the dispersed phase, and was influenced little with PTT as the dispersed phase. When the MMT content was increased from 2_wt% to 7_wt%, the crystallization of the PTT phase was slightly accelerated, whereas the crystallization of the PP phase was severely retarded, especially at lower temperatures. Moreover, the nucleation mechanism for the PP's crystallization changed from a thermal mode to an athermal one. In the polypropylene-graft-maleic anhydride (PP-g-MAH) compatibilized PTT/PP blends, with the addition of 2_wt% MMT during melt blending, the T _c (PTT) shifted 7.8°C to lower temperature and had a broadened exotherm, whereas the T _c (PP) shifted 17.1°C to higher temperature, with a narrowed exotherm. TEM analysis confirmed that part of the PP-g-MAH was combined with MMT during blending.     

卟啉铜接枝SiO2有机-无机复合材料及强的非线性折射率

通过卟啉配合物Meso-四(4-羧基苯基)卟啉铜(简称Cu(Ⅱ)-TCPP)中的羧基与γ-氨基丙基三乙氧基硅烷(NH₂(CH₂)₃Si(OC₂H₅)₃,KH550)中的氨基的相互化学作用,成功地把卟啉配合物接枝到KH550中,随着KH550中乙氧基的水解与聚合反应的进行,卟啉铜连接到固体介质中,从而大幅度提高了卟啉在无机固体介质中的掺杂浓度. 将反应产物与γ-(2,3-环氧丙氧基)丙基三甲氧基硅烷(CH₂CHCH₂O(CH₂)₃Si(OCH₃)₃,KH560) 相杂化,形成物化性能良好、连接卟啉的有机-无机复合材料. 用红外光谱表征了Cu(Ⅱ)-TCPP与KH550的化学反应产物,用紫外—可见吸收光谱研究Cu(Ⅱ)-TCPP的分子状态. 应用Z扫描技术研究不同Cu(Ⅱ)-TCPP掺杂浓度的复合材料的非线性光学性质,其三介非线性折射率n₂达-1.1161×10^-16 m²/W. 关键词： 非线性折射率 有机-无机复合材料 接枝 Meso-四(4-羧基苯基)卟啉铜     

(ZnSe)n(n=1,2)团簇结构及ZnSe分子热力学性质的理论计算

用密度泛函B3LYP方法、6-311 G基组对(ZnSe)n(n=1,2)分子体系进行了理论研究,得到(ZnSe)n(n=1,2)分子体系的基态电子状态的平衡几何Re、谐振频率、偶极矩和离解能De及不同温度、压力下的热力学函数值;设用总能量中的电子和振动能量近似代表ZnSe分子处于固态时的能量,用总熵中的电子和振动熵近似代表ZnSe分子处于固态时的熵,进而计算了Zn与Se反应的ΔH0、ΔS0、ΔG0,并由此计算出不同温度的反应平衡常数Kp.结果表明:在298~1150 K温度范围内,Zn与Se反应的自由能值均为负,且随着温度的升高,ΔG0值负的越多,表明在这个温度范围内反应能自发发生,而且自发趋势随温度的升高逐渐增大;平衡常数逐渐减小,即反应进行程度随温度的升高逐渐减小;ZnSe分子材料的导电性随压力增大而增强.     

Tip-surface interactions at redox responsive poly(ferrocenylsilane) (PFS) interface by AFM-based force spectroscopy

Poly(ferrocenylsilanes) (PFS) belong to the class of redox responsive organometallic polymers. Atomic force microscopy (AFM)-based single molecule force spectroscopy (SMFS) was used earlier to study single chain PFS response and redox energy driven single chain PFS molecular motors. Here we present further AFM investigations of force interactions between tip and a grafted PFS surface under potential control in electrochemical redox cycles. Typical tip-Au interaction is considered as reference in the force measurements. First the electrostatic component in the diffused double layer (DL) in NaClO₄ electrolyte environment was considered for a “grafted to” PFS, which dominated the interplay between the tip and sample surface. The DL forces can also hinder the physisorption of PFS chain onto the tip when the voltage was applied at −0.1 V. On the other hand, if the tip contacted the PFS surface prior to the electrochemical process, physisorption of PFS chains governed the overall interaction regardless of subsequently applied surface potential. In addition, prolonged contact time, t_c, may also contribute to the stability of tip-PFS bridging and detection of electrostatic forces between the tip-PFS interface. The results showed that tip-substrate interaction forces without PFS grafts have negligibly small force contributions under similar, electrochemically controlled, conditions used in single PFS chain based molecular motors.     

Phase-matched third-harmonic UV generation using low-order modes in a glass micro-fiber

We observe phase-matched third-harmonic generation at 355 nm in a low-order mode of a sub-micron diameter glass fiber. The third-harmonic signal exhibits a sharp resonance for a fiber diameter d = 0.49 ± 0.02 μm, in excellent agreement with the value d = 0.506 μm predicted by theory. The third-harmonic conversion efficiency is 2 × 10⁻⁶, and is limited by the pump power (1 kW) and effective fiber length (100 μm).     

Imprinting the nanostructures on the high refractive index semiconductor glass

The centimeter range one- and two-dimensional nanostructures of 70 nm pitch have been imprinted by hot pressing with a quartz, silicon or nickel mold, at 240 °C, onto the surface of Ge₂₀As₂₀Se₁₄Te₄₆ semiconductor glass. Excellent glass stability of this glass allows multiple re-pressing of the nano-structures. With increasing the Te/Se ratio in the glass formula, the refractive index reaches a value of 3.5 with an option of free electron absorption at elevated temperatures pointing out the use of such nanostructures in submicron and micron scale electronic devices/chips, moth eye structures and photonic crystals.