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排序方式: 共有121条查询结果,搜索用时 31 毫秒
71.
H. Arenhövel 《Nuclear Physics A》1975,247(3):473-494
The (NΔ) system has been investigated to see whether a quasi-bound state exists for which the lifetime of the Δ is considerably increased. The (NΔ) interaction using π- and ρ-meson exchange has been studied for various approximations. In particular, the Δ-nucleon mass difference and the Δ-width have been included leading to a complex (NΔ) potential. One finds that the (T = 2, JP = 2+ state is bound with a binding energy of 10 to 40 MeV depending on the type of potential used and on the regularization range. Furthermore, for this state the decay width of the Δ is strongly reduced by binding effects and the Pauli principle. The reduction amounts to a factor of three to five. 相似文献
72.
Generalized sum rules are derived by integrating the electromagnetic structure functions along lines of constant ratio of momentum and energy transfer. For non-relativistic systems these sum rules are related to the conventional photonuclear sum rules by a scaling transformation. The generalized sum rules are connected with the absorptive part of the forward scattering amplitude of virtual photons. The analytic structure of the scattering amplitudes and the possible existence of dispersion relations have been investigated in schematic relativistic and non-relativistic models. While for the non-relativistic case analyticity does not hold, the relativistic scattering amplitude is analytical for time-like (but not for space-like) photons and relations similar to the Gell-Mann-Goldberger-Thirring sum rule exist. 相似文献
73.
74.
Hartmuth Arenhövel 《Zeitschrift für Physik A Hadrons and Nuclei》1975,275(2):189-192
TheΔΔ-component of the deuteron is calculated in a full coupled channel calculation including a diagonalΔ-Δ-interaction and compared to the impulse approximation. Without a diagonalΔ-Δ-interaction both methods give very similar results while inclusion of theΔ-Δ-interaction leads to a decrease of the (ΔΔ)-probability of about 25%. The main uncertainties originate from limited knowledge of coupling constants and cut-off ranges. Accordingly the (ΔΔ)-probability varies between 0.3 and 1 percent. 相似文献
75.
Ryezayeva N Arenhövel H Burda O Byelikov A Chernykh M Enders J Griesshammer HW Kalmykov Y von Neumann-Cosel P Ozel B Poltoratska I Pysmenetska I Rangacharyulu C Rathi S Richter A Schrieder G Shevchenko A Yevetska O 《Physical review letters》2008,100(17):172501
Inclusive inelastic electron scattering off the deuteron under 180 degrees has been studied at the S-DALINAC close to the breakup threshold at momentum transfers q=0.27 fm;{-1} and 0.74 fm;{-1} with good energy resolution sufficient to map in detail the spin flip M1 response, which governs the starting reaction pn-->dgamma of big-bang nucleosynthesis over most of the relevant temperature region. Results from potential model calculations and (for q=0.27 fm;{-1}) from pionless nuclear effective field theory are in excellent agreement with the data. 相似文献
76.
Geis E Kohl M Ziskin V Akdogan T Arenhövel H Alarcon R Bertozzi W Booth E Botto T Calarco J Clasie B Crawford CB DeGrush A Donnelly TW Dow K Farkhondeh M Fatemi R Filoti O Franklin W Gao H Gilad S Hasell D Karpius P Kolster H Lee T Maschinot A Matthews J McIlhany K Meitanis N Milner RG Rapaport J Redwine RP Seely J Shinozaki A Sirca S Sindile A Six E Smith T Steadman M Tonguc B Tschalaer C Tsentalovich E Turchinetz W Xiao Y Xu W Zhang C Zhou Z Zwart T;BLAST Collaboration 《Physical review letters》2008,101(4):042501
We report new measurements of the neutron charge form factor at low momentum transfer using quasielastic electrodisintegration of the deuteron. Longitudinally polarized electrons at an energy of 850 MeV were scattered from an isotopically pure, highly polarized deuterium gas target. The scattered electrons and coincident neutrons were measured by the Bates Large Acceptance Spectrometer Toroid (BLAST) detector. The neutron form factor ratio GEn/GMn was extracted from the beam-target vector asymmetry AedV at four-momentum transfers Q2=0.14, 0.20, 0.29, and 0.42 (GeV/c)2. 相似文献
77.
Th. Walcher H. Arenhövel K. Aulenbacher R. Barday A. Jankowiak 《The European Physical Journal A - Hadrons and Nuclei》2007,34(4):447-461
We propose a method for polarising antiprotons in a storage ring by means of a polarised positron beam moving parallel to
the antiprotons. If the relative velocity is adjusted to v/c ≈ 0.002 the cross-section for spin-flip is as large as about 2 . 1013 barn as shown by new QED calculations of the triple spin cross-sections. Two possibilities for providing a positron source
with sufficient flux density are presented. A polarised positron beam with a polarisation of 0.70 and a flux density of approximately
1.5 . 1010 /(mm2 s) appears to be feasible by means of a radioactive 11C dc-source. A more involved proposal is the production of polarised positrons by pair production with circularly polarised
photons. It yields a polarisation of 0.76 and requires the injection into a small storage ring. Such polariser sources can
be used at low (100MeV) as well as at high (1GeV) energy storage rings providing a time of about one hour for polarisation
build-up of about 1010 antiprotons to a polarisation of about 0.18. A comparison with other proposals show a gain in the figure of merit by a factor
of about ten. 相似文献
78.
Within the framework of the hydrodynamic model the exact coupling constants of the coupling of the giant multipole resonances to the surface quadrupole oscillations of nuclei are derived. The differences to former variational calculations are discussed. It is found that the coupling constants for the terms linear in the surface variables are almost the same whereas the coupling constants for the quadratic terms differ appreciably. The influence on the photon absorption and scattering cross sections of spherical nuclei is discussed. 相似文献
79.
A comprehensive review of the role of nucleon resonances in nuclear structure is given with emphasis on the two-, three-, and four-nucleon systems and nuclear matter. 相似文献
80.
Scharschmidt J. Klapper H. Arenhövel H. 《Zeitschrift für Physik A Hadrons and Nuclei》1964,181(3):317-330
A calculation procedure is described which permits evaluation of the material functions (electrical conductivityσ and radiation densityu as a function of the heat flux potentialS)from the measured arc characteristicsE(I) andU(I) (field strength and radiated power per unit arc length as a function of current strength). Hereto must be employed the additional relationship of energy balance and the current transport equation. The procedure is applied to N2 and Ar. If furthermore the radial temperature distribution is known the temperature dependence ofσ, u.S andκ (thermal conductivity) may also be determined. In this way the material functions of the N2-plasma are evaluated from available measurements. 相似文献