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تسجيل مستخدم جديدPhoto- and electro-production of medium mass Lambda-hypernuclei
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The characteristic and selective nature of the electro-magnetic production of Lambda-hypernuclei in exciting states is demonstrated assuming the medium-mass targets 28Si, 40Ca, and 52Cr. Formalism of DWIA is used adopting the Saclay-Lyon, Kaon-MAID, Adelseck-Saghai, and Williams-Ji-Cotanch models for the elementary amplitudes and various nuclear and hypernuclear wave functions. The elementary amplitudes are discussed in detail presenting their basic properties and comparison with data. The unique features of the electro-magnetic production of Lambda-hypernuclei shown on examples are the slective excitation of unnatural parity highest-spin states (natural parity ones for the LS-closed targets) and a possibilty to investigate the Lambda single-particle energies including a spin-orbit splitting using variety of medium-mass targets.
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MF) approach, we show that the oblate deformation for $^{28}$Si nucleus may disappear when a $Lambda$ particle is added to this nucleus. We then discuss the rotational excitations of $^{25}_{Lambda}$Mg nucleus using the three-dimensional potential energy surface in the deformation plane obtained with the Skyrme-Hartree-Fock method. The deformation of $^{25}_{Lambda}$Mg nucleus is predicted to be slightly reduced due to an addition of $Lambda$ particle. We demonstrate that this leads to a reduction of electromagnetic transition probability, $B(E2)$, in the ground state rotational band. We also present an application of random phase approximation (RPA) to hypernuclei, and show that a new dipole mode, which we call a soft dipole $Lambda$ mode, appears in hypernuclei, which can be interpreted as an oscillation of $Lambda$ particle against the core nucleus.
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esonic decay (Lambda + N -> N + N) were extracted. The present results demonstrate an increase of the mesonic decay width due to a distortion of the pion wave function in nuclear medium for the first time. The ratios of the neutron- to proton-induced nonmesonic decay widths, Gamma_n(Lambda + n -> n + n)/Gamma_p(Lambda + p -> n + p), were evaluated by a direct comparison of the measured proton energy spectra with the calculated ones. No theoretical calculation which has been proposed so far can simultaneously account for both the nonmesonic decay widths and the Gamma_n/Gamma_p ratios in the present data.
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