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101.
R.Beck 《中国物理C(英文版)》2009,33(12)
The present focus of the CBELSA/TAPS experiment is on meson-photoproduction off the nucleon using polarized photons and polarized targets. Here first preliminary results on the reactions γ~→p~→→ pπ~0 and γ~→p~→pη for both circularly and linearly polarized photons and a longitudinally polarized target are presented. Preliminary results for the beam asymmetry Σ and the double polarization observable G have been extracted for both reactions using the linear polarization data. From the circular polarization data the observable E has been determined. Due to the near 4π angular coverage of the detector system these results cover almost the full solid angle. 相似文献
102.
Volker D. Burkert 《中国物理 C》2009,33(12):1043-1050
Recent measurements of nucleon resonance transition form factors with CLAS at Jefferson Lab are discussed. The new data confirm the assertion of the symmetric constituent quark model of the Roper as the first radial excitation of the nucleon. The data on high Q2 nπ+ production better constrain the branching ratios liNK and [3Nn. For the first time, the longitudinal transition amplitude to the S11(1535) was extracted from the nπ+ data. Also, new results on the transition amplitudes for the D13(1520) resonance are presented showing a rapid transition from helicity 3/2 dominance seen at the real photon point to helicty 1/2 dominance at higher Q2. I also discuss the status of the search for new excited nucleon states. 相似文献
103.
Kyungseon Joo 《中国物理 C》2009,33(12):1254-1256
We report the analysis status of single π0electroproduction in the resonance region to study the electromagnetic excitation of the nucleon resonances. The study is aimed at understanding of the internal structure and dynamics of the nucleon. The experiment was performed using an unpolarized cryogenic hydrogen target and 2.0 and 5.8 GeV polarized electron beam during the ele and e1-6 run periods with CLAS at Jefferson Lab. The new measurements will produce a data base with high statistics and large kinematic coverage for the hadronic invariant mass (W) up to 2.0 CeV in the momentum transfer (Q2) range of 0.3--6.0 GeV2. Preliminary results will be presented and compared with the various model calculations. 相似文献
104.
The reactions π-p →ηn and γ'p →ηP are investigated within a dynamical coupledJchannels model of meson production reactions in the nucleon resonance region. The meson-baryon channels included are πN, ηN, π△, σN, and pN. The direct wphotoproduction process is studied within a formalism based on a chiral constituent quark model approach, complemented with a one-gluon-exchange mechanism, to take into account the breakdown of the SU(6)0(3) symmetry. In the models search, the following known nucleon resonances are embodied: Sll (1535), $11(1650), Pll (1440), Pl1(1710), P13(1720), D13(1520), D13(1700), D15(1675), and F15(1680). Data for the π-p →ηnreaction from threshold up to a total center-of-mass energy of W ≈ 2 GeV are satisfactorily reproduced. For the photoproduction channel, two additional higher mass known resonances, P13 (1900) and F15 (2000), are also considered. However, reproducing the data for γ'p →ηP requires, within our approach, two new nucleon resonances, for which we extract mass and width. 相似文献
105.
We report our investigation on the octet baryon spectrum in the nonrelativistic quark model by taking into account the two-gluon exchange effect. The calculated octet baryon masses agree better with the experimental data. It is also shown that the two-gluon exchange interactions bring a significant correction to the Gell-Mann-Okubo mass formula. 相似文献
106.
Assuming that two weakly coupled oscillators are essentially nonlinear we construct the most suitable form of a shortened
3-dimensional system which describes behavior of solutions inside non-degenerate resonance zones. We analyze a model system
of that kind and establish the existence of limit cycles of different types and also the existence of nonregular attractors
which are explained by the existence of saddle-focus loops.
相似文献
107.
The exact solution of Schrödinger equation corresponding to a baryonic system is the main interest in the present work. We take into account both quadratic and Coulomb terms in the potential relation. Next, after presenting an exact solution, we have calculated the spin and isospin effects in both ground and excited states. The results are comparable with experimental data. 相似文献
108.
Based on electron transport theory,the performance of k x and k r filtered thermoelectric refrigerators with two resonances are studied in this paper.The performance characteristic curves between the cooling rate and the coefficient of performance are plotted by numerical calculation.It is shown that the maximum cooling rate of the thermoelectric refrigerator with two resonances increases but the maximum coefficient of performance decreases compared with those with one resonance.No matter which resonance mechanism is used(k x or k r filtered),the cooling rate and the performance coefficient of the k r filtered refrigerator are much better than those of the k x filtered one. 相似文献
109.
110.
Meng-Yin Zhou Lin Xu Lu-Chan Zhang Jiang Wu Yan-Bo Li Huan-Yang Chen 《Frontiers of Physics》2018,13(5):134101
We present a series of invisibility concentrators with simplified material parameters beyond transformation optics. One of them can achieve the perfect invisible effect at frequencies of Fabry–Pérot resonances, while others have very small scattering. The required materials are feasible in practice. Analytical calculations and numerical simulations confirm the functionalities of these devices. 相似文献