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The mass defect formula reflects the equivalence of mass and energy for bound nuclear systems. We study three-nucleon systems H and He, considering the neutron and proton as indistinguishable particles (AAA model) or taking into account the real masses of neutrons and protons (AAB model). We have focused on conceptual problems of the AAA model, which is widely used for 3 calculations. In particular, the AAA model is incompatible with the mass defect formula, which naturally corresponds to the AAB model. In addition, the AAA model has a cyclic permutation symmetry, which is breaking in the natural AAB model. The latter problem cannot be eliminated within the perturbative AAA approach, in which the mass difference effect is simulated by correcting the kinetic energy operator. Earlier it was reported that the accuracy of such AAA calculations is 1 keV. An example of the AAB calculation, we numerically estimate the effect of the difference between the neutron and proton masses on the energy calculated without any approximation with the accuracy of 0.1 keV. Another manifestation of the equivalence of mass and energy can be expressed by the formula . To show this dependence of the three-body energy on the nucleon mass, we performed realistic calculations within the AAA approximation, varying the averaged nucleon mass. The mass–energy compensation effect for the three-body Hamiltonian is shown. According to this, we have determined the effective nucleon mass required to compensate for the perturbative effect of a three-body potential. [ABSTRACT FROM AUTHOR]

Electronic and excitonic states in an InSb strongly flattened ellipsoidal quantum dot (QD) with complicated dispersion law are theoretically investigated within the framework of the geometric adiabatic approximation in the strong, intermediate, and weak quantum confinement regimes. For the lower levels of the spectrum, the square root dependence of energy on QD sizes is revealed in the case of Kane's dispersion law. The obtained results are compared to the case of a parabolic (standard) dispersion law of charge carriers. The possibility of the accidental exciton instability is revealed for the intermediate quantum confinement regime. For the weak quantum confinement regime, the motion of the exciton's center-of-gravity is quantized, which leads to the appearance of additional Coulomb-like sub-levels. It is revealed that in the case of the Kane dispersion law, the Coulomb levels shift into the depth of the forbidden band gap, moving away from the quantum confined level, whereas in the case of the parabolic dispersion law, the opposite picture is observed. The corresponding selection rules of quantum transitions for the interband absorption of light are obtained. New selection rules of quantum transitions between levels conditioned by 2D exciton center of mass vertical motion quantization in a QD are revealed. The absorption threshold behavior characteristics depending on the QDs geometrical sizes are also revealed. [ABSTRACT FROM AUTHOR]

An active target has been developed for studying the Hoyle like states in 16O. It is a position and time sensitive detector system based on the Low-Pressure Multy-Wire Proportional Chamber (LPMWPC) technique and Si detectors. The few Torr pressure of methyl ((OCH3)2CH2) serves as a working gas for the LPMWPC operation, and the oxygen atoms of the methyl molecules serve as an experimental target. The main advantage of this new target-detector system is a high sensitivity to the low-energy, highly ionizing particles, produced after photodisintegration of 16O, and the insensitivity to the γ-rays and low ionizing particles, which allows one to detect only the products of the nuclear reaction, which are studied. The threshold energies for detection of α particles and 12C nuclei are about 50 keV and 100 keV, respectively. Temporal and positional resolution of the LPMWPC modules was investigated with the use of the α-particle source. This paper discusses the architecture of the active target and the test results of the prototype MWPC detector. This installation has been constructed to study the cluster states at 15.1 MeV in 16O using the proton beams from the Yerevan proton cyclotron and the Compton backscattered photon beams of the ELI-NP facility. [ABSTRACT FROM AUTHOR]

The He nucleus is considered as the cluster α + n + n system. The excitation energies of the low-lying levels are calculated using the configuration-space Faddeev equations. The analytical continuation method in a coupling constant is applied for calculation of resonance parameters. The αn interaction is constructed to reproduce the results of R-matrix analysis for αn-scattering data. A realistic AV14 potential describes the nn interaction. Additional three-body potential adjusted by the ground state energy of He is used. The energies of the low-lying resonances of He (0, 0, 2) are reasonably reproduced by the calculations. [ABSTRACT FROM AUTHOR]

An α-cluster model is applied to study low-lying spectrum of the Be hypernucleus. The three-body ααΛ problem is numerically solved by the Faddeev equations in configuration space using phenomenological pair potentials. We found a set of the potentials that reproduces experimental data for the ground state (1/2) binding energy and excitation energy of the 5/2 and 3/2 states, simultaneously. This set includes the Ali-Bodmer potential of the version 'e' for αα and modified Tang-Herndon potential for αΛ interactions. The spin-orbit αΛ interaction is given by modified Scheerbaum potential. Low-lying energy levels are evaluated applying a variant of the analytical continuation method in the coupling constant. It is shown that the spectral properties of Be can be classified as an analog of Be spectrum with the exception of several 'genuine hypernuclear states'. This agrees qualitatively with previous studies. The results are compared with experimental data and new interpretation of the spectral structure is discussed. [ABSTRACT FROM AUTHOR]

The He hypernucleus is considered within the He + n + n cluster model. The hyperon—nucleon interaction is described by a one-boson-exchange potential that is constructed on the basis of the NSC97f model. Phenomenological potentials are used to describe the αΛ and αN interactions. For the He n interaction, use is made of the folding-model potential. The calculations of the hyperon binding energy in the ground state of the He hypernucleus on the basis of Faddeev equations in configuration space yield a result (5.35 MeV) that agrees well with preliminary experimental data (5.4 MeV). The problem of calculating the hyperon binding energy within the three-body approach is discussed. In calculating the energy spectrum of He, use is made of a version of the method of analytic continuation in the coupling constant. Low-lying excited states of this nucleus can be classified as an analog of the corresponding states of the 6He nucleus with allowance for the clustering of the He+ n+ n system in the 6He( Jπ)+Λ( s) form. [ABSTRACT FROM AUTHOR]

A high quality beam of linearly polarized photons of several GeV will become available with the coherent bremsstrahlung technique at JLab. We have developed a polarimeter which requires about two meters of the beam line, has an analyzing power of 20% and an efficiency of 0.02%. The layout and first of polarimeter test on the laser back-scattering photon beamat SPring-8/LEPS are presented. [ABSTRACT FROM AUTHOR]

The energy spectrum of Be is studied within the cluster model α + α + n. Configuration space Faddeev equations are applied to calculate energies of the bound state and resonances. LS coupling is used for partial wave analysis. The Be low-lying levels are classified as members of spin-flip doublets, in compliance with the total orbital momentum of the α + α + n system. The Be spectral data are well reproduced by the proposed model. [ABSTRACT FROM AUTHOR]

new computational method for solving the nucleon-deuteron breakup scattering problem has been applied to study the elastic nucleon-deuteron scattering on the basis of the configuration-space Faddeev-Noyes-Noble-Merkuriev equations. The Merkuriev-Gignoux-Laverne approach has been generalized for arbitrary nucleon-nucleon potentials and with an arbitrary number of partial waves. The nucleon-deuteron observables at the incident nucleon energy 3 MeV have been calculated using the charge-independent AV14 nucleon-nucleon potential including the Coulomb force for the proton-deuteron scattering. Results have been compared with those of other authors and with experimental proton-deuteron scattering data. [ABSTRACT FROM AUTHOR]

Inelastic neutron-deuteron scattering is studied on the basis of configuration-space Faddeev equations. Calculated are neutron-deuteron breakup amplitudes using AV14 nucleon-nucleon potential at incident neutron energy of 14.1 MeV. The results of calculations are presented for the differential cross sections under quasi free scattering and space-star configurations, and compared with those of the previous calculations and experimental data. The choice of the cutoff radius R for asymptotic conditions is discussed. [ABSTRACT FROM AUTHOR]