P-Odd effects in the γ+He4 → He4 + π0 reaction

P-Odd effects with the elastic photoinformation of neutral pions in He⁴ nuclei are due to the interference of the P-odd amplitude of weak interaction with the P-even amplitude of strong interaction, and originate only for polarized photons. It is shown that close to the reaction threshold P-odd effects should be small. The interference amplitude of the mechanisms corresponding to exchange with a Regge or-pole and a neutral Z-boson at high energies is studied. P-Odd effects in this case increase with increase of energy of the interacting particles and with the square of the imparted momentum. P-Odd effects due to interference of the s ingle-photon and Z-boson mechanisms are also investigated.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 71–76, September, 1978.     

T invariance and polarization effects in the reactions p+3He → π++4He and π++4He → p+3He

On the basis of T invariance, it is established that the dependence of the effective cross section for a binary reaction of the a+b → c+d type on the polarization vectors of primary particles a and b determines completely the polarization vectors and spin correlations for the same particles in the inverse reaction c+d → a+b induced by collisions between unpolarized primary particles c and d. By using the formalism of helicity amplitudes, polarization effects are studied in the process p+³He → π⁺+⁴He and in the inverse process π⁺+⁴He → p+³He. It is shown that, in the reaction π⁺+⁴He → p+³He, the spins of the final-state particles (proton and ³He nucleus) are strongly correlated. An expression for the correlation tensor is obtained for arbitrary values of the (p, ³He) emission angle.     

Coherent π0 photoproduction from 4He

Differential cross sections and beam asymmetries for coherent π⁰ photoproduction from ⁴He in the Δ energy-range have been measured with high statistical and systematic precision using both decay photons for identifying the process. The experiment was performed at the MAinz MIcrotron using the TAPS photon spectrometer and the Glasgow/Mainz tagged photon facility. The differential cross sections are in excellent agreement with predictions based on the DWIA if an appropriate parametrization of the Δ-nuclear interaction is applied. The beam asymmetries are interpreted in terms of degrees of linear polarization of collimated coherent bremsstrahlung. The expected increase of the degree of linear polarization with decreasing collimation angle is confirmed. Agreement with calculations is obtained on a few-percent level of precision in the maxima of the coherent peaks.     

超流体~4He中的声

超流体们~4He是一种特殊的液体,具有量子液体性质。超流体~4He中声传播的研究是发展量子流体动力学的重要方面,为研究凝聚态物理中的许多复杂问题,如声子、旋子及其它元激发等,提供了简便而有力的途径。这也表明声波作为研究物质性质的重要手段的能力。本文为近年来,研究超流体~4He中的声的总结。     

3He4He与H2分子碰撞的同位素效应研究

用公认精确度较高的密耦近似方法计算了入射能量E=0.5eV时惰性气体原子3He(4He)与H2分子替代碰撞体系的转动激发碰撞截面.通过分析3He(4He)-H2碰撞体系分波截面和微分截面的差异,总结出在氦原子的同位素替代情形下3He(4He)-H2碰撞体系分波截面和微分截面随分波数增加和同位素原子质量改变的变化规律.     

超流~3He、~4He溶液流体动力学方程——Ⅱ.超流~4He、~3He-A相溶液

在文[1]的基础上,我们继续用Lagrange不定乘子变分法推广Landau二流体超流理论到各向异性的超流氦溶液,得到关于超流4He、3He-A相的流体动力学方程。     

What is the physics behind the 3He–4He anomaly?

We show that coalescence of nucleons emitted prior to thermalization in highly excited nuclei can explain the anomaly of kinetic energies of helium clusters. A new coalescence algorithm has been included in the statistical approach to nuclear reactions formerly used to describe intermediate mass fragment production. Received: 24 September 1999 / Revised version: 22 November 1999     

超流~3He、~4He溶液流体动力学方程——Ⅰ.超流~4He、~3He-B相溶液

我们的工作是把Landau的二流体超流理论推广到超流~3He、~4He溶液,用Lagrangian不定乘子法研究超流~4He、~3He-B相溶液和超流~4He、~3He-A相溶液的动力学性质.本文先讨论~4He、~3He-B相溶液,严格导出其流体动力学方程.     

双超核ΛΛ5H,ΛΛ5He,ΛΛ4H,ΛΛ4He的研究

用少体理论方法对双Λ超核ΛΛ5He(ΛΛ5H)及ΛΛ4He(ΛΛ4H)的结合能进行了计算．结果表明,ΛΛ5He(ΛΛ5H)存在稳定的束缚态. 它们的双Λ结合能分别为对的研究的初步结果表明，它存在束缚态但相对于衰变不稳定．至于，结论是它不存在束缚态．     

4He闪烁裂变中子探测器时间响应

研制了可用于脉冲辐射场中子探测的4He闪烁裂变中子探测器,并对其时间响应进行了理论和实验研究。采用经验公式和蒙特卡罗方法模拟计算了不同厚度裂变靶产生的裂变碎片和不同能量中子产生的反冲4He核在4He气中的飞行时间,并依据卷积原理推导出探测器的时间响应计算公式。计算结果表明,探测器的波形上升时间约为19.5 ns,半高宽约31.0 ns。用ING-103型稠密等离子体聚焦装置(DPF)脉冲中子发生器对探测器的时间响应进行了实验测量,实验结果与理论值基本一致。     

Search for η-Mesic 4He with WASA-at-COSY

An exclusive measurement of the excitation functions for the dd → ³Hep π ^? and dd → ³Hen π ⁰ → ³Hen γ γ reactions was performed at the Cooler Synchrotron COSY-Jülich with the WASA-at-COSY detection system. The data were collected in two dedicated experiments in 2008 and in 2010. The experimental method and the current status of the analysis are presented.     

~4He超流密度分布研究

一种密度泛函理论用来研究当4He超流体流速u超过朗道临界流速vc时的不稳定性。发现有稳定的周期性密度波出现,其振幅正比于(u-vc)1/2,其波矢与旋子波矢一致。同时对纳米管道内氦流体进行了计算。     

4He闪烁裂变中子探测器的中子灵敏度

对4He闪烁裂变中子探测器的中子灵敏度进行了理论和实验研究。采用蒙特卡罗方法模拟了不同能量中子和不同厚度裂变靶产生的裂变碎片在4He中的能量沉积,计算结果表明:中子在4He气中的能量沉积曲线和裂变碎片的能量沉积曲线能够互补,从而使探测器对中子的能量响应变得更平坦;探测器的中子灵敏度为10-15 Ccm2量级。并对探测器的中子灵敏度进行了实验标定,实验结果与理论计算结果较为一致。     

Near threshold photoproduction of η mesons from 4 He

Photoproduction of - mesons from ⁴He has been measured for the first time. The experiment was performed at the Mainz Microtron (MAMI) using the TAPS photon spectrometer and the Glasgow/Mainz tagged photon facility. - mesons were identified in coincidence with recoil nucleons. Total and differential cross sections are presented in the photon energy range between threshold and 818 MeV. The exclusive data are used to determine the ratio of the elementary production cross sections on bound neutrons and protons, C_n/C_p = 0.68 - 0.02 - 0.09. In addition, upper limits for the total coherent cross section have been derived.     

π-~4He吸收后的核子谱

在两核子吸收的框架下,我们分析了静止的π~-以及60、100和220MeV的π~±介子在~4He上吸收后发射的核子谱。两核子吸收机制定量地符合现有实验。四核子的相空间计算与实验不符。     

固体^3He中的核磁有序和固体^4He中的超流动态

固体＾３Ｈｅ在１ｍＫ附近发生核磁有序，本文介绍了它的磁相图，物理性质和理论模型。固体＾４Ｈｅ中有可能存在像液体＾４Ｈｅ和液体＾３Ｈｅ中出现的超流动态，对理论预言和实验上的探索进行了评述。     

^4He超固体相变的比热证据

2004年,E．Kim等在一个固态氦的扭摆实验中发现,当温度降到约100mK以下时,扭摆的震荡周期突然减小．这意味着部分固态氦与大块晶格的运动退耦合,导致了转动惯量的突降．目前,学术界对上述现象的共识是,发生了超固体（supersolid）相变．3年以来,尽管在理论和实验两方面均有明显进展,但有关相变存在的热力学证据一直缺乏．最近,来自美国宾夕法尼亚州立大学的X．Lin等,在对固态氦的比热测量中,观察到一个与相变温度相应的比热峰,从而证实这是一个从正常固体相到超固体相的二级相变．     

Influence of D-state in 4He on S Factor for the 2H（d, γ）^4He Reaction

We employ a direct capture method to study the influence of D-state in ^4He on S factor for the ^2H（d,γ）^4He reaction, in which the D-state component of the colliding deuterons and D-state component in ^4He ground state are considered. The parameters of Woods-Saxon （WS） potentials are obtained by reproducing the binding energy of d-d （i.e. ^2H-^2H） system, and d-d elastic scattering phase shifts calculated by the resonating group method. The theoretical results are in good agreement with the experimental data at Ec.m〈 3 MeV. The impact of the D state probability in ^4He on the extrapolated value of the astrophysical S factor for ^2H（d, γ）^4He reaction is discussed.     

Observation of anomalously fast diffusion in 3He–4He solid solutions near the BCC-HCP transition

The pulsed NMR technique was used to investigate diffusion on the BCC-HCP phase-equilibrium and melting curves of a dilute solution of ³He in ⁴He. The contributions from all coexisting phases were identified using the spin-echo method. It is established that, along with the contributions from the equilibrium BCC and HCP phases or from bulk liquid (in the melting curve measurements), there is an additional diffusional process that is characterized by an anomalously high diffusion coefficient. It is found that the latter is close to the diffusion coefficient in liquid helium, while the diffusion itself is spatially restricted. The observed effect may be caused by the formation of liquid droplets in the course of the BCC-HCP transition.