排序方式: 共有117条查询结果,搜索用时 281 毫秒
51.
We extract the x dependence of the valence nonsinglet u - d distribution function in the nucleon from the lowest few moments calculated on the lattice, using an extrapolation formula which ensures the correct behavior in the chiral and heavy quark limits. We discuss the implications for the quark mass dependence of meson masses lying on the JPC = 1– - Regge trajectory. 相似文献
52.
Keiji Hayashi Daisuke Tanaka Harumi Araki Tomoki Maruyama Daisuke Matsumura Kazuho Toyoda Noriyuki Tsuji 《Applied Surface Science》2009,255(24):9581-9584
Ion-current difference measurement by light intensity modulation (ICD) is introduced as a convenient method to characterize a purified beam of momentum-controlled neutral free radicals produced by photo-deionization of a negative ion beam for the purpose of surface-reaction-selective device processing. The ICD setup developed in this study to estimate the number flux of the photo-deionized neutral particles exhibited the high precision, sensitivity, and spatial resolution. 相似文献
53.
Jun Xu Ling Yang Jiaxin Mei Wei Li Ling Xu Kunji Chen 《Solid State Communications》2005,133(9):565-568
Hydrogenated amorphous SiC thin films deposited at low substrate temperature (100 °C) show the different bonding configurations and microstructures which depend on the carbon concentrations in the films controlled by the gas ratio R of methane to silane during the deposition. Photoluminescence characteristics are investigated for these samples with different structures. A strong luminescence in red light region can be observed for samples deposited with low gas ratio R which is significantly reduced its intensity with increasing the carbon concentrations in the films. On the other hand, the luminescence bands located at blue-green light region are detected under UV light excitation for samples deposited with high gas ratio R, which can be associated with the existence of amorphous SiC clusters in the films. 相似文献
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55.
S. Momota M. Kanazawa A. Kitagawa S. Sato Y. Nojiri 《The European physical journal. Special topics》2007,150(1):315-316
The longitudinal and transverse momentum (PL and PYenT) distributions of projectile-like fragments, which were produced with an Ar beam and various targets (C, Al, Nb, Tb, Au),
were measured at E=290A MeV. No significant target effects are found in P L distribution. The width of PT distribution increases with target mass. It is plausible that this result is explained by the deflection of orbit arising
from Coulomb repulsion. The nuclear structural effects are observed in isotopic and isotonic distributions of production cross-sections
of fragments, which are derived from observed momentum distributions. 相似文献
56.
A. Schäfer 《The European Physical Journal A - Hadrons and Nuclei》2007,32(4):371-377
Hadron structure physics has in recent years reached a level of precision which allows for a change of perspective. Model-based
arguments are often quite unreliable. However, meanwhile they can be more and more replaced by controlled and systematic QCD
approaches. The story of the strange electric form factor, which provided much of the motivation for the PAVI Conference series
provides a typical example to illustrate this statement. However, high-precision theory is technically very challenging and
progress is, therefore, unpleasantly slow. This fact and the present status in general is illustrated by a few typical examples. 相似文献
57.
Jian-Zhong Ma Thomas Guhr Tilo Wettig 《The European Physical Journal A - Hadrons and Nuclei》1998,2(1):87-98
The statistical properties of the spectrum of the staggered Dirac operator in an SU(2) lattice gauge theory are analyzed
both in the bulk of the spectrum and at the spectrum edge. Two commonly used statistics, the number variance and the spectral
rigidity, are investigated. While the spectral fluctuations at the edge are suppressed to the same extent as in the bulk,
the spectra are more rigid at the edge. To study this effect, we introduce a microscopic unfolding procedure to separate the
variation of the microscopic spectral density from the fluctuations. For the unfolded data, the number variance shows oscillations
of the same kind as before unfolding, and the average spectral rigidity becomes larger than the one in the bulk. In addition,
the short-range statistics at the origin is studied. The lattice data are compared to predictions of chiral random-matrix
theory, and agreement with the chiral Gaussian Symplectic Ensemble is found.
Received: 6 November 1997 / Revised version: 19 January 1998 相似文献
58.
J.M.B. Shorto P.R.S. Gomes J. Lubian L.F. Canto S. Mukherjee L.C. Chamon 《Physics letters. [Part B]》2009
We propose a new technique to analyze total reaction cross sections. In this technique, which has been previously applied to fusion reactions, the experimental data are used to build a dimensionless reaction function, which does not depend on the system size or details of the optical potential. In this way, total reaction cross sections for different systems can be directly compared. We employ this technique to perform a systematic study of reaction cross sections of weakly bound systems in different mass ranges, and compare their reaction functions with the ones of tightly bound systems with similar masses. We show that breakup reactions and neutron transfers in halo systems lead to large reaction functions, well above the ones of typical tightly or weakly bound stable systems. 相似文献
59.
In this work we theoretically study using continuum-discretized-coupled channel (CDCC) theory, the resonant breakup of 16O by comparison with a recent measurement. The ground state Asymptotic Normalization Coefficient (ANC) and the alpha spectroscopic factor of 16O are evaluated in this work. The peripheral aspect of resonance breakup through a 2+ unbound state has been also studied. 相似文献
60.