Search for charm production in direct decays of the ?(1S) resonance

The production ofD ^*(2010)⁺ andJ/ mesons and prompt leptons has been investigated ine ⁺ e ^– interactions at the (1S) resonance energy. The data were collected at the storage ring DORIS II at DESY with the ARGUS detector. We obtain upper limits of BR^dir ( (1S)D ^*(2010)^±+X)<0.019>x _p >0.2) and BR^dir ((1S)J/+X)<>^–3, both at the 90% confidence level. From the prompt lepton analysis, a model dependent limit of BR^dir ((1S)Y _c +X)<0.034>Y _c denoting a charm-containing particle) is derived.Supported by the German Bundesministerium für Forschung und Technologie, under contract number 054DO51P     

?(x) Matrices via New Yang-Baxterization

Several new ?(x) matrices as solutions of Yank-Baxter equations are found via a developed trigonometric Yang-Baxterization for three eigenvalues. The consistency conditions of the new trigonometric Yang-Baxterization are obtained explicitly.     

DNA双螺旋结构是怎样发现的?(续)

在沃森和克里克对糖一磷酸基骨架有了一个合理的构想后，就着手解决碱基配对的问题．沃森在戴维逊（Davidson．J．N）写的《核酸的生物化学》一书中，找到了碱基的化学结构式，它们是氨基和烯醇互变异构形式（amino and enol tautomeric forms）．沃森在《双螺旋》一书中谈到了他建立模型的意图，他写道：“我想把那些位于中心的碱基安排在这样一种位置上，     

S?(12)群表示的填充与强衰变

本文讨论了(3/2)^-,(1/2)^-,(7/2)⁺等共振态在S?(12)群表示中的填充及其强衰变,发现16016,35100两个表示中的(3/2)^-粒子不能衰变到(1/2)⁺和0^-.通过改变运动方程质量项的符号使表示的宇称改变,就能将((3/2)^-,8)和((1/2)^-,1)填在572表示中,从而使它们能衰变到(1/2)⁺和0^-。但是,((3/2)^-,1)和(7/2)⁺仍然不能通过S?(12)对称的有效顶点衰变,本文还详细分析了S?(12)在基本粒子分类和强衰变中的成功之处与局限性,并讨论了这种局限性产生的原因。     

公式F=ma中的力从哪来?(之三)

（上接2005年第11期第786页） 3 文化差异 如我们所见,力的概念定义了一种文化.在先前发表的此系列的专栏文章（Physics Today,2004年10月,第11页以及2004年12月,第10页）中1）,我说明了通过对力这一概念的诠释（实际上是关于力的附加假设）,公式F=ma是如何被赋予意义的.这样的诠释有点民间传说的味道.它既包含了在适当条件下我们可以从近代〈物理〉2）基础得到的近似,也包含了从经验中抽象出的略嫌粗放的推广（例如关于摩擦力和弹性行为的所谓的“定律”）.     

公式F=ma中的力从哪来?(之二)

2 赋予合理性 我在先前的专栏（Physics Today,2004年10月,第11页）1）里论述了那些关于力和质量的假设是怎样为公式F=ma的内涵赋予实质的.我将这一系列的假设称为“力的文化”.我提到,尽管“力的文化”中的一些元素经常被称为“定律”,但是用近代物理的观点来看却显得非常奇怪.在此,我将讨论其中某些假设是在什么样的情况下如何作为近代《物理》2）基本原理之必然推论出现的--或者根本就不是!     

L?(1)群的引力规范场球对称静态解

寻找引力规范理论场方程的严格解要比寻找Einstein场方程的严格解更为困难。但是,对某些物理问题来说,能够求得牛顿型近似解和后牛顿型的近似解就足够了。本文研究了一种Lorentz群和U(1)群为规范群的引力规范理论,求得了带电粒子的球对称静场的特殊有挠解,并求得了有挠的一阶近似解。 关键词：     

Kinetics of glass transition and thermal stability of?Se58Ge42?xPbx?(9≤x≤20) glasses

Se₅₈Ge_42−x Pb _x (9≤x≤20) glasses have been prepared using conventional melt quenching technique. Differential Scanning Calorimetric (DSC) measurements show single glass transition and double crystallization, which indicate the occurrence of phase separation in the samples. The phases present in the samples were identified using XRD. The kinetics of the glass transition has been studied in terms of the variation of glass transition temperature with composition and heating rate. In addition to this, activation energy of the glass transition (E _t ) has also been evaluated and its composition dependence is also investigated. The thermal stability of these glasses has been investigated using various stability criteria: Deiztal first glass criterion, ΔT, Saad and Poulain weighted thermal stability, H′ and the S-parameter. The values of these parameters were obtained using various characteristic temperatures such as the glass transition temperature, T _g , the onset temperature of crystallization, T _c , and the peak crystallization temperature, T _p . The values of stability parameters show that the phase corresponding to second crystallization is more stable than the phase corresponding to first one. The stability in terms of the lead (Pb) content has been determined considering the values of stability parameters of the phase corresponding to second peak. It was found that the stability increases with the lead content.     

Study of K~*(892)~0 and ?(1020) meson production in proton–proton and Pb–Pb collisions at ■=2.76 TeV

In this paper, we describe a study of charged particle yield as a function of pTfor K~*(892)~0 and ?(1020) mesons in proton–proton(pp) and Pb–Pb collisions at ■=?2.76 Te V in the central rapidity region of |y|0.5, in a pTrange of ?pT15 Ge V c~(-1) in pp collisions and in a pT range of 0??pT??20 Ge V c~(-1) in Pb-Pb collisions. We also investigated a very important ratio,the nuclear modification factor, to study the effects of the medium in the most central region, i.e.0%–5% centrality. For data simulation, we used the EPOS-LHC and EPOS-1.99 models. To check the validity of these models' simulations, we compared the data obtained from these Monte Carlo simulation programs with ALICE experimental data for ■=?2.76 Te V. It was concluded that the models' predictions for the ?-meson in pp and for the most central Pb-Pb collisions disagreed with the ALICE data, and that the difference increased with pT. This may be connected with the essential role of collective parton behaviors which could not have been taken into account by the models. For K~(*0) mesons, both programs gave almost the same predictions,and with pTin the interval pT??3 Ge V c~(-1), the predictions were very close to the experimental data. Both models gave higher predictions for the soft pTinterval and lower predictions for the hard interactions. The values of the RAAdistributions were lower than unity and both models were very close to the ALICE data. It is very interesting that the models were not able to describe the pTdistributions, but they gave good predictions for their ratios. This may possibly be due to parton collective behaviors. We observed some additional suppression of K~(*0) at low values of pT with respect to f-mesons, which may be related to the role of the masses of the particles in soft interactions. The rising trend for R_(AA) in the region from pT=?10 Ge V c~(-1) to 20 Ge V c~(-1) observed by the ALICE experiment was absent for the f-mesons.     

Superconductivity and ferromagnetism in EuFe?(As(1-x)P(x))?

Superconductivity and ferromagnetism are two antagonistic cooperative phenomena, which makes it difficult for them to coexist. Here we demonstrate experimentally that they do coexist in EuFe?(As(1-x)P(x))? with 0.2 ≤ x ≤ 0.4, in which superconductivity is associated with Fe 3d electrons and ferromagnetism comes from the long-range ordering of Eu 4f moments via Ruderman-Kittel-Kasuya-Yosida (RKKY) interactions. The coexistence features large saturated ferromagnetic moments, high and comparable superconducting and magnetic transition temperatures, and broad coexistence ranges in temperature and field. We ascribe this unusual phenomenon to the robustness of superconductivity as well as the multi-orbital character of iron pnictides.     

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。     

《物理》杂志怎样办成为一个名副其实的社会主义期刊?(读者来信摘登)

“作为社会主义自然科学期刊之一的《物理》怎么办？”许多读者来信参加这个讨论,表示他们对这一问题的关心和支持,对我们的帮助很大．但是,要把《物理》杂志办成为一个名副其实的社会主义自然科学期刊,还要做很多的工作．这不仅是一个理论问题,更重要的是一个实践问题,是两条路线斗争的问题．希望广大读者继续参加讨论,尤其是对我们的编辑工作,提出具体的批评和建议,使我们的工作沿着毛主席的革命路线更加迅速地前进．     

爆轰产物物态方程(Ⅱ)--爆轰的ZND理论不成立吗?(下)

用Jones公式检验爆轰的ZND理论是另一种检验方法.这种检验方法不需要知道爆轰产物物态方程的形式,只需知道其存在即可.百密一疏,美国科学家用这种方法检验得出的结论是ZND理论不成立.更稹密地运用这种方法得出的检验结论是爆轰的ZND理论成立.     

Influence of Self-Interaction ofσ Meson to the Equation of State of Nuclear Matter

In the relativistic σ-ωmodel, the influence of the parameters in self-interaction of a meson to the equation of state of normal nuclear matter, especially, to incompressibility, effective mass, and coupling constants, is studied in detail. We find that these parameters have an intense relationship to the property of nuclear matter. At the same time , we study the relation between the binding energy and pressure of relativestic △-resonance nuclear matter and temperature using using above results in the relativistic σ-ω-π model,and it is interesting to compare it to our prior work. In all these studies, the vacuum fluctuation on nucleon, △-isobar, and σmeson is considered.     

Analysis of the causes of formation of negative loss factors

I-IatroductionStatisticalEnergyAnalysis(SEA)isakindofeffective,simpleanddirectapproachforan-alyzingvibrationandsound,andithasbeenfoundwidelyapplicationsinanalysisofmechanicalnoiseandvibrationcolltrolsince198osl1-4].However,forgeneralindustrialmachineswhichalwayconsistofcomPlexandheaVystructures,thedeterminationmethodsofSEAparametersintheclassicalSEAtheoryareinapplicable[5]because:(1)SEAparametersofthesekindsofstructuresaredifficulttoobtainfromthetheory(2)theconditionofconservativeandweak…     

Teleportation of an arbitrary mixture of diagonal states of multiqudit

This paper proposes a scheme to teleport an arbitrary mixture of diagonal states of multiqutrit via classical correlation and classical communication. To teleport an arbitrary mixture of diagonal states of N qutrits, N classically correlated pairs of two qutrits are used as channel. The sender （Alice） makes Fourier transform and conditional gate （i.e., XOR（3） gate） on her qutrits and does measurement in appropriate computation bases. Then she sends N ctrits to the receiver （Bob）. Based on the received information, Bob performs the corresponding unitary transformation on his qutrits and obtains the teleported state. Teleportation of an arbitrary mixture of diagonal states of multiqudit is also discussed.     

Analysis of Frequency Spectrum of Laser-Induced Vibration of Microbeam Resonators

The vibration phenomenon during pulsed laser heating of micro-beams is investigated. The beam is made of silicon and is heated by a laser pulse with a non-Gaussian temporal profile and with an ultrashort pulse duration of 2ps, which incites vibration due to the thermoelastic damping effect. This coupled thermoelastic problem is solved using an analytical-numerical technique based on the Laplace transformation. The damping ratio and resonant frequency shift ratio of beams due to the air damping effect and the thermoelastic damping effect are also examined and discussed.     

Improvement of Synchronizability of Scale-Free Networks

We investigate the factors that affect synchronizability of coupled oscillators on scale-free networks. Using the memory Tabu search （MTS） algorithm, we improve the eigen-ratio Q of a coupling matrix by edge intercrossing. The numerical results show that the synchronizatlon-improved scale-free networks should have distinctive both small average distance and larger clustering coefficient, which are consistent with some real-world networks. Moreover, the synchronizability-improved networks demonstrate the disassortative coefficient.