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61.
H. V. Klapdor-Kleingrothaus 《Foundations of Physics》2003,33(5):813-829
Double beta decay is indispensable to solve the question of the neutrino mass matrix together with oscillation experiments. Recent analysis of the most sensitive experiment since nine years—the HEIDELBERG-MOSCOW experiment in Gran-Sasso—yields a first indication for the neutrinoless decay mode. This result is the first evidence for lepton number violation and proves the neutrino to be a Majorana particle. We give the present status of the analysis in this report. It excludes several of the neutrino mass scenarios allowed from present neutrino oscillation experiments—only degenerate scenarios and those with inverse mass hierarchy survive. This result allows neutrinos to still play an important role as dark matter in the Universe. To improve the accuracy of the present result, considerably enlarged experiments are required, such as GENIUS. A GENIUS Test Facility has been funded and will come into operation by early 2003. 相似文献
62.
63.
采用微扰静态(PSS)模型近似处理极化和结合能效应,并引入了相对论效应、能量损失效应和库仑偏转效应修正的ECPSSR理论是描述直接库仑电离过程最成功的理论,但对于低能离子入射时, 其结果明显低于实验值. 采用联合分离原子(USA)模型替代ECPSSR中的PSS模型,考虑分子轨道效应得到了基于USA模型的电离理论——MECUSAR理论. 对部分碰撞系统进行了计算,得到的碰撞截面与实验结果基本符合. 结合OBKN(Oppenheimer-Brinkman-Kramers formulas of Nikolae
关键词:
X射线产生截面
离子-原子碰撞
电子俘获 相似文献
64.
O. Kavatsyuk C. Mazzocchi Z. Janas A. Banu L. Batist F. Becker A. Blazhev W. Brüchle J. Döring T. Faestermann M. Górska H. Grawe A. Jungclaus M. Karny M. Kavatsyuk O. Klepper R. Kirchner M. La Commara K. Miernik I. Mukha C. Plettner A. Płochocki E. Roeckl M. Romoli K. Rykaczewski M. Schädel K. Schmidt R. Schwengner J. Żylicz 《The European Physical Journal A - Hadrons and Nuclei》2007,31(3):319-325
The β decay of the very neutron-deficient isotope 101Sn was studied at the GSI on-line mass separator using silicon detectors for recording charged particles and germanium detectors
for γ-ray spectroscopy. Based on the β-delayed proton data the production cross-section of 101Sn in the 50Cr + 58Ni fusion-evaporation reaction was determined to be about 60nb. The half-life of 101Sn was measured to be 1.9(3)s. For the first time β-delayed γ-rays of 101Sn were tentatively identified, yielding weak evidence for a cascade of 352 and 1065keV transitions in 101In. The results for the 101Sn decay as well as those from previous work on the 103Sn decay are discussed by comparing them to predictions obtained from shell model calculations employing a new interaction
in the 88Sr to 132Sn model space. 相似文献
65.
A. Faessler 《The European Physical Journal A - Hadrons and Nuclei》2007,31(4):424-428
The neutrinoless double-beta decay is not allowed in the Standard Model (SM) but it is allowed in most Grand Unified Theories
(GUTs). The neutrino must be a Majorana particle (identical with its antiparticle) and must have a mass to allow the neutrinoless
double-beta decay. Apart of one claim that the neutrinoless double-beta decay in 76Ge is measured, one has only upper limits for this transition probability. But even the upper limits allow to give upper limits
for the electron Majorana neutrino mass and upper limits for parameters of GUTs and the minimal R-parity violating supersymmetric model. One further can give lower limits for the vector boson mediating mainly the right-handed
weak interaction and the heavy mainly right-handed Majorana neutrino in left-right symmetric GUTs. For that, one has to assume
that the specific mechanism is the leading one for the neutrinoless double-beta decay and one has to be able to calculate
reliably the corresponding nuclear matrix elements. In the present contribution, one discusses the accuracy of the present
status of calculating the nuclear matrix elements and the corresponding limits of GUTs and supersymmetric parameters. 相似文献
66.
Multiple ionization of argon accompanied by electron loss and capture of 0.22-6.35 MeV C^q+ ions
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In this paper a projectile ions recoil ions coincidence technique is employed to investigate the target ionization and projectile charge state changing processes in the collision of 0.22-6.35 MeV Cq^+ (q = 1 - 4) ions with argon atoms. The partial cross section ratios of the double, triple, quadruplicate ionization to the single ionization (or the single capture) of argon associated with single electron loss (or single electron capture) by the projectile are measured and compared with the previous experimental results. In the present experiment, it is observed that the ratios of ionization cross sections R associated with single loss and single capture depend strongly on the projectile charge state and vary significantly with different reaction channels as impact energy increases. In addition, this paper gets empirical scaling laws for the ionization cross section ratios R corresponding to the projectile single loss and finds that the ratios of the double ionization to the single ionization associated with single electron capture remain constant in the present energy range. 相似文献
67.
A.L. Barabanov 《The European Physical Journal A - Hadrons and Nuclei》1999,6(4):373-374
It is shown that new spin-orbit-like terms appear in the effective nonrelativistic weak Hamiltonian for nucleon provided
that nuclear potential is taken into account. Arguments for their considerable enhancement, in particular, in relativistic
nuclear model of Walecka are advanced.
Received: 29 July 1999 相似文献
68.
Sukhendusekhar Sarkar 《Pramana》1999,53(3):469-472
We examine the possible role of electron-capture on the thermally populated first 2+ excited state of 44Ti in hot astrophysical environments pertaining to post explosive nucleosynthesis supernova debris. We find in a simple schematic
model that the astrophysical weak interaction rate for electron-capture decay of 44Ti can depend considerably on temperature and hence on time. We propose a time varying decay rate for the evolving supernova
debris and demonstrate its consequence for the 44Ti mass yield of the supernova Cas A, observed through the measured 1.157 MeV γ-ray flux from the electron-capture decay of
44Ti. 相似文献
69.
D. Dane Quinn 《Nonlinear dynamics》2009,57(4):623-633
The response of a nonlinear, damped Jeffcott rotor with anisotropic stiffness is considered in the presence of an imbalance.
For sufficiently small external torque or large imbalance, resonance capture or rotordynamic stall can occur, whereby the
rotational velocity of the shaft is unable to increase beyond the fundamental resonance between the rotational and translational
motion. This phenomena provides a mechanism for energy transfer from the rotational to the translational mode. Using the method
of averaging a reduced-order model is developed, valid near the resonance, that describes this resonant behavior. The equilibrium
points of these averaged equations, which correspond to stationary solutions of the original equations and rotordynamic stall,
are described as the applied torque, damping, and anisotropy vary. As the anisotropy increases, assumed to arise from increasing
shaft cracks, the torque required to eliminate the possibility of stall increases. However, when the system is started with
zero initial conditions, the minimum torque required to pass through the resonance is approximately constant as the anisotropy
increases. The predictions from the reduced-order model are verified against numerical simulations of the original equations
of motion. 相似文献
70.
恒星能量下俘获截面非常难于直接测量.因此,通常借助于非直接方法或从最低能量下的实验数据外推到天体物理感兴趣能区.首先证明了用渐近归一化常数方法得到的结果近似与模型无关.因此,转移反应的渐近归一化常数方法处理提供了一可靠的途径用以确定恒星能量下的俘获截面. 鉴于此优点, 用渐近归一化常数方法计算了10Be(n,γ)11Be反应的俘获截面. 11Be是一个众所周知的具有两弱束缚态的晕核.作为一个典型的例子,演示了俘获到晕态的辐射俘获截面明显增大, 证明了入射中子波函数与晕的伸展尾部有较大重叠是俘获截面异常增大的原因. 相似文献