Results 1 - 10 of 64
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[en] The three-body resonance energies of the strange dibaryon are studied with the (bar K)NN-πYN coupled-channels Faddeev equations. Our resonance energies are compared with those of an effective potential approach (EPA), where a coupling to the πYN channel is simulated by an effective (bar K)N potential, and the spectator momentum in the πYN Green function is neglected. About a 30% reduction of the binding energies due to neglecting the spectator momentum in the πYN Green's function is observed.
[en] We present a pedagogical study of the commonly employed Speed-Plot (SP) and Time-delay (TD) methods for extracting the resonance parameters from the data of two particle coupled-channels reactions. Within several exactly solvable models, it is found that these two methods find poles on different Riemann sheets and are not always valid. We then develop an analytical continuation method for extracting the nucleon resonances within a dynamical coupled-channel formulation of the pi-N and gamma-N reactions. The main focus is on resolving the complications due to the coupling with the unstable pi-Delta; rho-N; sigma-N channels which decay into pi-pi-N states. By using the results from the considered exactly solvable models, explicit numerical procedures are presented and verified. As a first application of the developed analytical continuation method, we present the nucleon resonances in the S11 and S31 partial waves extracted within a recently developed coupled-channels model of pi-N react
[en] Recently, experimental research was carried out on the angular distribution of (γ, π+) reaction in p shell nuclei by Tohoku University group. Here, analysis is performed on C-13 (γ, π+) B-13 (gr). In the (γ, π+-) reaction, a Kroll-Ruderman term becomes the main term at low energy, and the reaction is a good probe for the research on nuclear structure by sigmatau type excitation. As the treatment of nuclear structure, the analysis of (γ, π) has been carried out, using the transient density adjusting electron scattering phenomenologically. However, all the transient density cannot be determined uniquely, rather (γ, π) reaction and electron scattering give the information on nuclear structure complementarily. Here, how the effect of core polarization studied in detail in electron scattering works in the (γ, π) reaction is investigated. The contribution of exchange current is small in both M1 and E2, and core polarization plays a main role in the region of the momentum transfer of high electromagnetic form factor. The effective Hamiltonian of (γ, π) and the nuclear model adopted are explained. To the angular distribution of C-13 (γ, π+) B-13 (gr), in the front part, M1, and in the back part, E2 contributed mainly. The effect of core polarization improved the difference in the back part by reducing E2. (Kako, I.)
[en] A unitary coupled-channels model is presented for investigating the decays of heavy mesons and excited meson states into three light pseudoscalar mesons. The model accounts for the three-mesons final state interactions in the decay processes, as required by both the three-body and two-body unitarity conditions. In the absence of the Z-diagram mechanisms that are necessary consequence of the three-body unitarity, our decay amplitudes are reduced to a form similar to those used in the so-called isobar-model analysis. We apply our coupled-channels model to the three-pions decays of a1(1260), pi2(1670), pi2(2100), and D0 mesons, and show that the Z-diagram mechanisms can contribute to the calculated Dalitz plot distributions by as much as 30% in magnitudes in the regions where f0(600), rho(760), and f2(1270) dominate the distributions. Also, by fitting to the same Dalitz plot distributions, we demonstrate that the decay amplitudes obtained with the unitary model and the isobar model can be rather different, particularly in the phase that plays a crucial role in extracting the CKM CP-violating phase from the data of B meson decays. Our results indicate that the commonly used isobar model analysis must be extended to account for the final state interactions required by the three-body unitarity to re-analyze the three-mesons decays of heavy mesons, thereby exploring hybrid or exotic mesons, and signatures of physics beyond the Standard Model.
[en] We briefly summarize the current understanding of nuclear electromagnetic current. The validity and the accuracy of the description of nuclear system in terms of meson and nucleon degrees of freedom and also a possible signature on the break down of the above picture are discussed. (author)
[en] A dynamical coupled-channels formalism is used to investigate the η-meson production mechanism on the proton induced by pions, in the total center-of-mass energy region from threshold up to 2 GeV. We show how and why studying exclusively total cross section data might turn out to be misleading in pinning down the reaction mechanism.
[en] The device of the present invention can measure an appropriate flow rate in a reactor core continuously also during a transient period. Namely, a reactor recycling system comprises jet pumps operated by high pressure/high speed coolants pressurized by recycling pumps of two systems. The difference of the total energy of the fluid between the upstream and the downstream of diffusers of the jet pumps is determined and utilized. It is judged that the flow rate of the jet pump turns from a normal flow to a reverse flow based on the difference of the total energy. In this case, the flow rate of the jet pump is defined as a negative value, which is added to the flow rate of the jet pump in a normal flowing state except for the flow rate described above. According to the device of the present invention, the flow rate of the reactor core can be measured continuously and appropriately even when the flow of the jet pump is reversed as well as in a case of a normal flow. (I.S.)
[en] The formulas of beta-ray angular distributions for the allowed transition are derived in Elementary Particle Treatment of nuclei by taking into account the Coulomb interaction between the beta-particle and the residual nucleus, and also by requiring the gauge invariance. It is shown that the present formulas are closely related with the conventional ones. (auth.)
[en] The scattering length and effective range of the πΣ channel are studied in order to characterize the strangeness S = -1 meson-baryon scattering and the Λ(1405) resonance. We examine various off-shell dependence of the amplitude in dynamical chiral models to evaluate the threshold quantities with the constraint at the (bar K)N threshold. We find that the πΣ threshold parameters are important to the structure of the Λ(1405) resonance and provide further constraints on the subthreshold extrapolation of the (bar K)N interaction.
[en] Highlights: • This bioreactor for microalgae provides the optimized arrangement of internal LEDs. • Flashing-light effect of the photosynthesis was demonstrated. • A cell density of 67% of that of the ideal condition was measured. • Numerical simulations predict the largest growth rate of 10.18 g/L/day. - Abstract: In this study, a photobioreactor for mass-culturing microalgae was developed. Because of the optimized arrangement of internal light-emitting diode (LED) illumination, a major advantage to this reactor is that the volume of the reactor vessel is not limited. Using Dunaliella tertiolecta as the microalgae, the bioreactor displayed the flashing-light effect of the microalgae photosynthesis process. This phenomenon was achieved using a series of blue and red LEDs set at appropriate positions within the reactor to evenly distribute the light intensity. Our experimental results suggested that the maximum cell density in the culture experiment was 1.88 × 10"3 cells L"−"1, which is approximately 67% of the maximum density under ideal conditions. The harvest yield of the algae was estimated by a numerical model using measured parameters; it was predicted that the bioreactor developed in this study can attain a high growth rate of D. tertiolecta by controlling the distance between LEDs.