Charmed andϕmeson decay constants from 2+1-flavor lattice QCD

On a lattice with 2+1-flavor dynamical domain-wall fermions at the physical pion mass,we calculate the decay constants of D_s^* , D^* ,and φ .The lattice size is 48^3×96 ,which corresponds to a spatial extension of -5.5 fm,with a lattice spacing of a\approx a≈0.114 fm.For the valence light,strange,and charm quarks,we use overlap fermions at several mass points close to their physical values.Our results at the physical point are f_D=213(5) MeV, f_Ds=249(7) MeV, f_D^*=234(6) MeV, f_Ds^*=274(7) MeV,and f_Ds=241(9) MeV.The couplings of D^* and D_s^* to the tensor current( f_V^T )can be derived from ratios f_D^*^T/f_D^*=0.91(4) and f_Ds^*^T/f_Ds^*=0.92(4) ,respectively,which are the first lattice quantum chromodynamics(QCD)results.We also obtain ratios f_D^*/f_D=1.10(3) and f_Ds^*/f_Ds=1.10(4) ,which reflect the size of heavy quark symmetry breaking in charmed mesons.Ratios f_Ds/f_D=1.16(3) and f_Ds^*/f_D^*=1.17(3) can be taken as a measure of SU(3)flavor symmetry breaking.     

面内场和静态偏磁场作用下条畴和泡畴的稳定性

实验研究面内场H_in和静态偏磁场H_b作用下,(111)面磁泡膜内条畴的消失过程。保持H_b恒定,增加H_in,测量条畴消失场H_s^*和泡畴消失场H_k^*与面内场方向β的变化关系。计及立方磁晶各向异性的影响,建立H_in和H_b共同存在时的条畴稳定性理论。定性解释了实验的主要特点。导出黑、白条畴同时消失时的角度 β_n=1/3(2nπ±arc cos│3/(2^1/2)(M_sH_b)/K₁│)(n=0,±1,±2,…)与实验基本符合。 关键词：     

立方磁晶各向异性对面内磁场中条畴和磁泡稳定性的影响

在八个(111)面磁泡膜上,观察了施加面内(in-plane)磁场后在不同晶轴方向上条状畴的消失过程,测量了条畴消失场H_s^*和磁畴消失场H_k^*与面内磁场的方向的关系。本文计及立方磁晶各向异性,完善了面内磁场中条畴的稳定性理论。用该理论定性地解释了实验结果的主要特点。导出了H_s^*与立方各向异性及面内场方向的两种近似的理论关系,它们分别适用于面内场方向靠近和不十分靠近〈110〉晶轴的情形。它们和实验结果是大致符合的。在〈110〉晶轴上,理论关系具有下列简单的形式:H_k^*<110>=H_s^*<110>=H_k{1+(k₁/2K_u)-[al/h(4πM_s/H_k)²]^2/3},此式与实验结果符合得相当好。 关键词：     

电子衍射图自动标定中初基解的判据

在电子衍射图的自动标定中,将距中心最近的两个衍射斑点与计算出的两个倒易矢量r₁^*及r₂^*对比,可得r₁^*×r₂^*=Au。不过,有时会出现与非初基倒易平面胞对应的非初基解。对于简单布喇菲点阵,显然A=1是初基解的判据。对于有心布喇菲点阵的初基解,在u,v,w三个指数的不同组合的情况下,A也有确定值。 关键词：     

相互作用能量参数对A(B1/21B1/22)O3系统有序畴形成的影响

本文利用有序-无序相变理论讨论了A(B_1/2¹B_1/2²)O₃系统中的有序-无序相变,半定量地研究了在A(B_1/2¹B_1/2²)O₃系统中相互作用能参数对形成B¹:B²=1:1有序畴的影响,理论计算结果与实验结果基本一致。 关键词：     

矢量介子及其激发态的讨论

在Regge唯象下, 首先研究自旋-宇称多重态中六个介子质量间的关系式. 运用验证后的关系式, 重点计算基态矢量介子多重态(1³S₁)中尚未观测到的双重粲-底介子 B_c^*的质量. 还计算了径向激发态2³S₁多重态的介子质量和轨道激发态1³G₅介子九重态的质量. 根据计算结果结合实验数据和其他理论进行讨论, 建议在6355 MeV附近寻找和研究 B_c^*介子, 将 D(2600)和 D_s1(2700)分别作为主要成分为 nc(2³S₁)和 sc(2³S₁)的态进行研究; 分别在5812, 5917, 6896 MeV附近寻找矢量介子第一径向激发态 B^*(2S), B_s^*(2S)和 B_c^*(2S). 建议将 ω₅(2250)安排在1³G₅介子九重态的同位旋标量态, 实验上在2259 MeV附近进一步研究 ρ₅(2350)的性质, 在2438 MeV附近寻找和研究 φ₅(1³G₅). 研究结果对于相关介子的自旋-宇称安排和通过实 验寻找新的介子激发态具有重要的参考价值. 关键词： Regge唯象 矢量介子 质量谱     

薄膜硅/晶体硅异质结电池中本征硅薄膜钝化层的性质及光发射谱研究

本文采用甚高频等离子体化学气相沉积技术 (VHF-PECVD) 制备薄膜硅/晶体硅异质结电池中的本征硅薄膜钝化层, 光发射谱 (OES) 测量技术研究了硅薄膜沉积过程中等离子体发光谱随时间的变化. 结果表明: 在实验优化条件下等离子体发光谱很快达到稳定 (大约25 s), 并且SiH^*/H_α^* 的比值随时间变化较小, 避免了生长过程中硅薄膜结构的不均匀性, 这主要是SiH₄没有完全耗尽避免了SiH₄的反向扩散. 进一步研究了沉积参数对稳态发光谱和硅薄膜性质的影响, 结果表明: 随着硅烷浓度增加, H_α^*峰强度减小, SiH^*峰强度增加, 薄膜从微晶转变成非晶, 非晶硅薄膜钝化效果好; 随着沉积气压增大, H_α^*和 SiH^*峰强度先增加后减小, 高气压下H_α^*和 SiH^*峰强度下降主要是反应前驱物的聚合形成高聚合物, 不利于形成高质量的硅薄膜, 因此钝化效果下降; 随着反应功率密度增加, H_α^*和 SiH^*峰强度增大, 当功率密度为150 mW/cm² 趋于饱和, 硅薄膜的致密度和钝化效果也开始下降, 50 mW/cm²的低功率密度下硅薄膜钝化效果差可能是由于原子H 浓度低, 不能完全钝化单晶硅表面的悬挂键. 关键词： 薄膜硅 异质结 光发射谱 钝化     

圆管潜射流生成偶极子涡特性实验

利用溢流恒压装置产生具有稳定出流速度的圆管潜射流, 结合染色液流态显示方法, 在多种射流无量纲潜深d/H、雷诺数Re以及限制数C的组合下, 实验研究了该潜射流动量在有限深密度均匀流体中的演化特性, 其中d为射流潜深, H为水深. 研究表明, 当C<1时潜射流表现为深水特征, 而当1≤ C<2时潜射流表现为过渡特征, 在这两种情况下均不产生任何形式的大尺度相干结构; 当2≤ C<10时潜射流表现为浅水特征, 而C≥10时潜射流表现为极浅水特征, 在这两种情况下均产生大尺度的偶极子涡结构. 对极浅水特征潜射流, 在各种无量纲潜深下, 偶极子涡结构的无量纲形成时间t_f^*与无量纲射流时间T_inj^*均满足相同的正比例关系; 对浅水特征潜射流, 当d/H=0.5时, t_f^*与T_inj^*满足某种线性关系, 但对其他无量纲潜深, t_f^*与T_inj^*之间无明显规律. 关键词： 圆管潜射流 限制数 偶极子涡结构 形成时间     

四氟化碳分子电离解离过程中的异构化动力学

采用离子动量成像谱仪研究了能量为1.0 ke V的电子束碰撞条件下CF₄分子的解离动力学.实验上,对解离离子的三维动量进行了成像测量,通过离子飞行时间关联谱识别了CF₄²⁺异构化生成F₂⁺分子的两个通道:F₂⁺+CF₂⁺与CF⁺+F₂⁺+F,得到了两个通道的离子动能及动能释放分布.对于其中的三体解离通道,我们进一步采用Dalitz图与Newton图等三体动力学分析方法对解离碎片的动量关联进行了分析.该通道以两个带电离子的背对背出射为主,中性的F原子作为旁观者只得到极小的反冲动量.     

无扩散相变中界面动力学的唯象理论及其应用

固态相变中相界面或畴界面的平均运动速度V与有效相变驱动力△G＇(相变驱动力△G与相界面运动阻力△G_R之差)之间的关系可表示为V=φ(△G—△G_R)。当有单向变化的外场(场强为ξ,变化速率为ξ)作用于相变系统并能诱导相界面运动时,就会产生母相/新相间的转变。在相变过程中同时叠加一个交变应力时,则可计算得界面动力学关系V=φ(△G—△G_R)与相变过程内耗Q^-1、相关的模量亏损(△M/M)、相变速率dF/dξ、相变应变ε₀间的关系为 [d lnφ(△G-△G_R)/d(△G-△G_R)]= Q^-1ω/n²M(dF/dξ)ξ = (△M/M)ω/nMε₀(dF/dξ)ξ, 以及 (△M/M)/Q^-1=ε₀/n。此处ω为交变应力的圆频率,M为与振动模式有关的弹性模量,n为应力与界面运动的耦合因子。因此,界面动力学关系式的通解为 V = ∑(±n)/(α≠-1) A_α exp{[(△G-△G_R)/△G_α^*]^{α+ 1}/(α+ 1)} +∑(m)/(β₀) A_β[(△G-△G_R)/△G_β^*]^β 此处n,m为正整数。上式中的各项参数可由实验数据确定。此外,(△M/M)/Q^-1的等式还可用于判别相变过程的模量亏损中有无声子模软化的贡献。 关键词：     

Revisiting the Twist-3 Distribution Amplitudes of K Meson Within the QCD Background Field Approach

In the present paper, we investigate the kaon twist-3 distribution amplitudes (DAs) φ_p,σ^K within the QCD background field approach. The SU_f(3)-breaking effects are studied in detail under a systematical way, especially the sum rules for the moments of φ_p,σ^K are obtained by keeping all the mass terms in the s-quark propagator consistently. After adding all the uncertainties in quadrature, the first two Gegenbauler moments of φ_p,σ^K are a_K,p¹ (1 GeV) = -0.376_-0.148^+0.103, a_K,p²(1 GeV) = 0.701_-0.491^+0.481, a_K,σ¹ (1 GeV) = -0.160_-0.074^+0.051, and a_K,σ²(1 GeV) = 0.369_-0.149^+0.163, respectively. Their normalization parameters μ_K^p|1 m GeV = 1.188_-0.043^+0.039 GeV and μ_K^σ|1 m GeV = 1.021_-0.055^+0.036 GeV. A detailed discussion on the properties of φ_p,σ^K moments shows that the higher-order s-quark mass terms can indeed provide sizable contributions. Furthermore, based on the newly obtained moments, a model for the kaon twist-3 wavefunction Ψ_p,σ^K(x,k⊥) with a better end-point behavior is constructed, which shall be useful for perturbative QCD calculations. As a byproduct, we make a discussion on the properties of the pion twist-3 DAs.     

Production Rate of Ds+Ds- at φ(4030)

By using a generalized relativistic quark pair creation model (QPCM), the hadronic decay processes of φ(4030), assigned as the 3S state of cc, are investigated. The relative rates of φ(4030) → DD, DD^*+DD^*, D^*D^*,and in particular D_s⁺D_s^- are calculated and compared with data. The nodes of the radially excited wavefunctions of charmonium states are found to be significant for these decay processes. Considering the SU(3) suppression factor of ~3 for the s quark pair creation relative to the u and d quarks, we obtain σ(e⁺e^- → φ4(4030) → D_s⁺D_s^-) ~ 0.9 nb.     

The Soliton-Like and instant on-Like Solutions of the Generalized ξφ6 Model

The well-known ξφ⁶ scalar field model is extended to a more general form. It is shown that there exist various types (both topological and nontopological) of the soliton-like and instanton-like solitary wave solutions for the generalized ξφ⁶ model. Some special types of solutions of the conventional ξφ⁶ model can be transformed to that of the extended ξφ⁶ model with an arbitrary constant and then various cnoidal waves of the extended modei are also obtained. Especially, a large number of model-independent soliton-like, instanton-like and cnoidal wave solutions, which are the same as that of the usual ξφ⁶ model, are allowed.     

The Signatures of the Neutral Top-Pion at the NLC and the Tevatron in Topcolor-Assisted MWTC Model

The neutral top-pion π_t⁰ can couple to the gluons and the photons through the top quark triangle-loop. we calculate the corrections of the neutral top-pion π_t⁰ to the tt production cross section in topcolor-assisted multiscale walking technicolor model. We find that, for a heavy neutral top-pion, the corrections are quite significant. For m_t = 175 GeV, 5 GeV ≤ m_t¹ ≤ 20 GeV and M_πt = 350 GeV, the relative correction Δσ/σ₀ is larger than 10% which might be observed at a high-luminosity Tevatron. We further estimate the production cross section of π_t⁰ at the NLC experiment. We find that the production rate is significantly large. The neutral top-pion π_t⁰ may be detected in future e⁺e^- linear collider experiments.     

Global Electroweak Fit and Its Implication for Z'

Among the Z-pole observables, AFB^（0,b） and Ae display moderately large standard deviations from the Standard Model predictions. This result can be interpreted as independent experimental evidence for new physics beyond the SM, even if the 125 GeV Higgs-like boson at the LHC is ultimately confirmed as the SM Higgs. A recalculated global electroweak fit with a model-independent Z＇ shows that Z＇ can simultaneously suppress AFB（0,b） and Ae at the Z-pole, and reduce the largest deviation from 2.6σ in SM to 1.0σ in our scenario. The Z＇ fitting results also support a negative S parameter.     

反应物分子初始振动激发对H+CH~+→C~++H_2反应的影响

在CH_2~+体系的电子基态势能面上运用准经典轨线方法,研究了当碰撞能E=500 me V时,反应物分子的振动激发对H(~2S)+CH~+(X~1Σ~+)→C+(~2P)+H_2(X1_gΣ~+)反应的反应概率、反应截面和立体动力学性质的影响.分别计算了两矢量相关k-j′的P(θ_r)分布,三矢量相关k-k′-j′的P(φr)分布以及反应产物的四个极化微分截面.结果表明,产物分子转动角动量不仅在Y轴方向有取向效应,还定于Y轴的正方向.并且发现,随着振动量子数的增加,对反应体系产物分布的影响就越明显.     

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采用Langmuir探针法结合发射光谱法对螺旋波诱导的低压氢等离子体进行诊断,根据Druyvesteyn 方法和日冕模型分析电子能量几率函数(EEPF)、有效电子温度(Teff)、电子密度(ne)及激发态氢原子密度(nH*)随实验参数的变化规律.结果表明:随射频功率(Prf)、气压(p)和约束磁场(B)的增大,EEPF峰位由高能向低能移动,Teff 下降;当Prf从25W增大至35W左右时,ne发生跳跃增长,而nH*始终随Prf增大线性增长;随p增大,ne和nH*都呈现先增加后减小的变化规律;随B增强,ne线性增长,而nH*先增大后减小.     

Magnetic Excitations and the Curie Temperature of Decamethylchromocenium Tetracyanoethylenide

We describe the molecular ferromagnet decamethylchromocenium tetracyanoethanide [C_rC_p2^*] [TCNE] by a quasi-one-dimensional alternating-spin model with ferromagnetic exchange interaction. The spin-wave theory is used to discuss the magnetic excitation of the molecular ferromagnet. We obtain the magnetizations corresponding to different external magnetic fields without interchain exchange interaction which is consistent with the experimental results. The formula of the Curie temperature T_c is obtained by using the thermodynamic Green's function method. It is found to be related to the spin of donors, to the intrachain exchange interaction and to the spatial anisotropic parameter. The result obtained by this T_c formula is consistent with the experimental result T_c = 3.6 K for [C_rC_p2^*][TCNE].     

一个新的自由能函数对介电高弹薄膜的多组等双轴预拉伸下力电耦合实验的预测

当介电高弹聚合物薄膜被施以面内等双轴预拉伸后, 受到厚度方向的电压作用时, 薄膜在力场和电场共同作用下产生大变形. 电场采用Maxwell应力分析, 力场采用橡胶弹性模型分析. 拟合这类变形的常用橡胶弹性模型主要有Neo-Hookean, Arruda-Boyce, Gent等模型. 这些模型对实验数据的定量拟合存在不同程度的偏差. 通过对实验数据的分析, 结合数学方法, 提出了一个新的自由能函数模型. 通过该模型对VHB4905介电高弹聚合物薄膜的多组等双轴预拉伸电力耦合实验进行拟合, 并以Neo-Hookean, Gent模型作为对照, 结果与实验数据拟合很好, 比对照模型的偏差明显缩小.     

Equilibrium dynamics of the sub-Ohmic spin-boson model under bias

Using the bosonic numerical renormalization group method, we studied the equilibrium dynamical correlation function C(ω) of the spin operator σ_z for the biased sub-Ohmic spin-boson model. The small-ω behavior C(ω) ∝ω~s is found to be universal and independent of the bias ε and the coupling strength α(except at the quantum critical point α = αc and ε = 0). Our NRG data also show C(ω) ∝χ~2ω~s for a wide range of parameters, including the biased strong coupling regime(ε = 0 and α α_c), supporting the general validity of the Shiba relation. Close to the quantum critical point αc,the dependence of C(ω) on α and ε is understood in terms of the competition between ε and the crossover energy scale ω_0~*of the unbiased case. C(ω) is stable with respect to ε for ε《ε~*. For ε》ε~*, it is suppressed by ε in the low frequency regime. We establish that ε~*∝(ω_0~*)~(1/θ)holds for all sub-Ohmic regime 0≤s 1, with θ = 2/(3s) for 0 s≤1/2 and θ = 2/(1 + s) for 1/2 s 1. The variation of C(ω) with α and ε is summarized into a crossover phase diagram on the α–ε plane.