共查询到20条相似文献,搜索用时 15 毫秒
1.
A.J.Buchmann 《中国物理C(英文版)》2009,33(12)
A group theoretical derivation of a relation between the N →△ charge quadrupole transition and neutron charge form factors is presented. 相似文献
2.
The sea quark contributions to the nucleon electromagnetic form factors of the up,down and strange quarks are studied with the nonlocal chiral effective Lagrangian.Both octet and decuplet intermediate states are included in the one loop calculations.Compared with the strange quark form factors,although their signs are the same,the absolute value of the light quark form factors are much larger.For both the electric and magnetic form factors,the contribution of the d quark is larger than of the u quark.The current lattice simulations of the light sea quark form factors are in between our results for the u and d quarks. 相似文献
3.
The nonlocal chiral effective theory is applied to investigate the electromagnetic and strange form factors of nucleons. The bubble and tadpole diagrams are included in the calculation. With the contributions from bubble and tadpole diagrams, the obtained electromagnetic form factors are close to the results without these contributions as long as the low energy constants \begin{document}$ c_1 $\end{document} ![]()
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and \begin{document}$ c_2 $\end{document} ![]()
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are properly chosen, while the magnitudes of strange form factors become larger. The electromagnetic form factors are in good agreement with the experimental results, while the magnitudes of strange form factors are larger than the lattice data. 相似文献
4.
We study the asymptotic behavior of the ratio of Pauli and Dirac electromagnetic nucleon form factors, F2/F1, in time-like region, for different parametrizations built for the space-like region. We investigate how fast the ratio F2/F1 approaches the asymptotic limits according to the Phragmèn-Lindel?f theorem. We show that the QCD-inspired logarithmic behavior
of this ratio results in very far asymptotics, experimentally unachievable. This is also confirmed by the normal component
of the nucleon polarization, Py, in e+ + e-↦N + ˉ (in collisions of unpolarized leptons), which is a very interesting observable, with respect to this theorem. Finally
we observe that the 1/Q parametrization of F2/F1 contradicts this theorem. 相似文献
5.
We review the current experimental and theoretical status of the proton electromagnetic form factors. 相似文献
6.
O. V. Teryaev 《Frontiers of Physics》2016,11(5):111207
Nucleon scattering by the classical gravitational field is described by the gravitational (energy-momentum tensor) form factors (GFFs), which also control the partition of nucleon spin between the total angular momenta of quarks and gluons. The equivalence principle (EP) for spin dynamics results in the identically zero anomalous gravitomagnetic moment, which is the straightforward analog of its electromagnetic counterpart. The extended EP (ExEP) describes its (approximate) validity separately for quarks and gluons and, in turn, results in equal partition of the momentum and total angular momentum. It is violated in quantum electrodynamics and perturbative quantum chromodynamics (QCD), but may be restored in nonperturbative QCD because of confinement and spontaneous chiral symmetry breaking, which is supported by models and lattice QCD calculations. It may, in principle, be checked by extracting the generalized parton distributions from hard exclusive processes. The EP for spin-1 hadrons is also manifested in inclusive processes (deep inelastic scattering and the Drell–Yan process) in sum rules for tensor structure functions and parton distributions. The ExEP may originate in either gravity-proof confinement or in the closeness of the GFF to its asymptotic values in relation to the mediocrity principle. The GFFs in time-like regions reveal some similarity between inflation and annihilation. 相似文献
7.
8.
DONG Yu-Bing 《中国物理C(英文版)》2010,34(9)
The effect of the two-photon exchange on the deuteron electromagnetic form factors is estimated based on an effective Lagrangian approach. A numerical estimate calculation of the effect is discussed. In particular, the effect on the polarization observables is analyzed. 相似文献
9.
The effect of the two-photon exchange on the deuteron electromagnetic form factors is estimated based on an effective Lagrangian approach. A numerical estimate calculation of the effect is discussed. In particular, the effect on the polarization observables is analyzed. 相似文献
10.
A simple mechanism of replica symmetry breaking for spin-glass, as suggested by Parisi, has been used to solve the anisotropic
spin-glass model of Sherrington and Ghatak. Temperature variation of the correlation parameters and the resulting variations
with the temperature of the thermodynamic quantities like internal energy, specific heat and entropy have been evaluated.
It is found that the anisotropy has considerable effect on the properties of the spin system. At low temperatures, the specific
heat varies asT
2. However, the entropy is positive for temperatures above 0.1°K, which is a considerable improvement on the results of Sherrington
and Ghatak. The results are expected to be in good agreement with experiment or computer simulation studies near transition
temperatures. 相似文献
11.
《Physics letters. [Part B]》2001,511(1):33-39
We present a study of proton and neutron electromagnetic form factors for the recently proposed Goldstone-boson-exchange constituent quark model. Results for charge radii, magnetic moments, and electric as well as magnetic form factors are reported. The calculations are performed in a covariant framework using the point-form approach to relativistic quantum mechanics. All the predictions by the Goldstone-boson-exchange constituent quark model are found to fall remarkably close to existing experimental data. 相似文献
12.
Using a Thomas-Fermi type picture of the nucleon as a dense system of quarks and antiquarks, we give a rationale for the ‘dipole’
nature, scaling and other characteristics of the nucleon electromagnetic form factors. Similar considerations are then given
for the electromagnetic structure of the pion. 相似文献
13.
A period of rapidly accelerating expansion is expected in the early Universe implemented by a scalar field slowly rolling down along an asymptotically flat potential preferred by the current data. In this paper, we point out that this picture of the cosmic inflation with an asymptotically flat potential could emerge from the Palatini quadratic gravity by adding the matter field in such a way to break the local gauged conformal symmetry in both kinetic and potential terms. 相似文献
14.
15.
As a new example of spontaneous pattern formation in many-body systems, we examine the collective means by which a close-packed disk crystal reacts to the presence of a single oversized impurity disk. Computer simulation has been used for this purpose; it creates the jammed impurity-containing packings by a kinetic particle-growth algorithm. Hexagonal primitive cells with periodic boundary conditions were employed, and the natural number 3n
2 of disks (including the impurity) ranged upt to 10,800. For impurity diameter 1.2 times that of the other disks, the patterns of observed crystal perturbation displayed several remarkable features. Particle displacements relative to the unperturbed triangular crystal possess local irregularity but long-range coherence. The symmetry of the coherent patterns preserved that of the hexagonal cell for rapid growth, but was lower for slower growth. The final jammed packings contain rattler disks of the sort known to apper in random disk packings. Finally, the area increase induced by the presence of a fixed-size impurity appears to grow without bound as the system size (i.e., 3n
2) itself increases. 相似文献
16.
Deuteron electromagnetic form factors and tensor polarization observables in the framework of the hard-wall AdS/QCD model 下载免费PDF全文
We study the electromagnetic form factors and tensor polarization observables of the deuteron in the framework of the hard-wall AdS/QCD model. We find a profile function for the bulk twist \begin{document}$\tau=6$\end{document} ![]()
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vector field, which describes the deuteron on the boundary and fix the infrared boundary cut-off of AdS space in accordance with the ground state mass of the deuteron. We obtain the deuteron charge monopole, quadrupole, and magnetic dipole form factors and tensor polarization observables from the bulk Lagrangians for the deuteron and photon field interactions. We plot the momentum transfer dependence of the form factors and tensor polarization observables and compare our numerical results with those in the soft-wall model and experimental data. 相似文献
17.
18.
M.P. Rekalo E. Tomasi-Gustafsson 《The European Physical Journal A - Hadrons and Nuclei》2003,16(4):563-567
We discuss the applicability of pQCD to the elastic scattering of electrons on protons and deuterons. We analyze the Q2-dependence of the reduced deuteron form factor, taking into account the recent data on the electric proton form factor and
we find that the value of the QCD-scale parameter Λ differs essentially from the value Λ = 0.1 GeV, previously found using
the dipole parametrization of the electromagnetic nucleon form factors GE and GM. Moreover, the predicted scaling behavior of the reduced deuteron form factor cannot be recovered in the Dirac and Pauli
representations for the nucleon electromagnetic form factors.
Received: 14 October 2002 / Accepted: 12 November 2002 / Published online: 11 March 2003
RID="a"
ID="a"Permanent address: National Science Center KFTI, 310108 Kharkov, Ukraine.
RID="b"
ID="b"e-mail: etomasi@cea.fr
Communicated by V.V. Anisovich 相似文献
19.
Yi Yu Yaohui Chen Hao Hu Weiqi Xue Kresten Yvind Jesper Mork 《Laser \u0026amp; Photonics Reviews》2015,9(2):241-247
Nanostructures that feature nonreciprocal light transmission are highly desirable building blocks for realizing photonic integrated circuits. Here, a simple and ultracompact photonic‐crystal structure, where a waveguide is coupled to a single nanocavity, is proposed and experimentally demonstrated, showing very efficient optical diode functionality. The key novelty of the structure is the use of cavity‐enhanced material nonlinearities in combination with spatial symmetry breaking and a Fano resonance to realize nonreciprocal propagation effects at ultralow power and with good wavelength tunability. The nonlinearity of the device relies on ultrafast carrier dynamics, rather than the thermal effects usually considered, allowing the demonstration of nonreciprocal operation at a bit‐rate of 10 Gbit s−1 with a low energy consumption of 4.5 fJ bit−1.