20,027 research outputs found

    On the momentum-dependence of KK^{-}-nuclear potentials

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    The momentum dependent KK^{-}-nucleus optical potentials are obtained based on the relativistic mean-field theory. By considering the quarks coordinates of KK^- meson, we introduced a momentum-dependent "form factor" to modify the coupling vertexes. The parameters in the form factors are determined by fitting the experimental KK^{-}-nucleus scattering data. It is found that the real part of the optical potentials decrease with increasing KK^- momenta, however the imaginary potentials increase at first with increasing momenta up to Pk=450550P_k=450\sim 550 MeV and then decrease. By comparing the calculated KK^- mean free paths with those from KnK^-n/KpK^-p scattering data, we suggested that the real potential depth is V080V_0\sim 80 MeV, and the imaginary potential parameter is W065W_0\sim 65 MeV.Comment: 9 pages, 4 figure

    The properties of kaonic nuclei in relativistic mean-field theory

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    The static properties of some possible light and moderate kaonic nuclei, from C to Ti, are studied in the relativistic mean-field theory. The 1s and 1p state binding energies of KK^- are in the range of 739673\sim 96 MeV and 226322\sim 63 MeV, respectively. The binding energies of 1p states increase monotonically with the nucleon number A. The upper limit of the widths are about 42±1442\pm 14 MeV for the 1s states, and about 71±1071\pm 10 MeV for the 1p states. The lower limit of the widths are about 12±412\pm 4 MeV for the 1s states, and 21±321\pm 3 MeV for the 1p states. If V030V_{0}\leq 30 MeV, the discrete KK^- bound states should be identified in experiment. The shrinkage effect is found in the possible kaonic nuclei. The interior nuclear density increases obviously, the densest center density is about 2.1ρ02.1\rho_{0}.Comment: 9 pages, 2 tables and 1 figure, widths are considered, changes a lo

    Preparation of MAl2O4: Eu2+, Sm3+ (M = Ca, Sr, Ba) Phosphors by the Combustion Method and their Luminescent Properties

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    A series of MAl2O4: Eu2+, Sm3+ (M = Ca, Sr, Ba) phosphors was prepared by the combustion method, and the influence of these alkaline earth metals on the structure and luminescent performances for these phosphors was investigated. A relationship was established between their composition, crystallization capacity and luminescent properties. The results show that the CaAl2O4: Eu2+, Sm3+ and SrAl2O4: Eu2+, Sm3+ phosphors exhibit monoclinic crystal systems and that the BaAl2O4: Eu2+, Sm3+ phosphor exhibits a hexagonal structure. The alkaline earth metal has a positive effect on the crystallization process, the heat treatment procedure and the luminescent properties of the corresponding phosphors. According to the order Ca > Sr > Ba, the maximum emission wavelengths of the corresponding phosphors are found at 505 nm, 490 nm and 478 nm, and the relevant colours of emitted light are between blue and green, which indicates that there is a clear blue shift in the emission spectra, but their excitation spectra show almost no difference. The decay curve shows that the afterglow intensity and time are not only related to the activating processes and the hole transport, but also to the phase structure and the grain size,which is in the order Sr>Ca>Ba.Keywords: Long afterglow, alkaline earth aluminates, spectra, combustion metho

    A hybrid algorithm for predicting median-plane head-related transfer functions from anthropometric measurements

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    Since head-related transfer functions (HRTFs) represent the interactions between sounds and physiological structures of listeners, anthropometric parameters represent a straightforward way to customize (or predict) individualized HRTFs. This paper proposes a hybrid algorithm for predicting median-plane individualized HRTFs using anthropometric parameters. The proposed hybrid algorithm consists of three parts: decomposition of HRTFs; selection of key anthropometric parameters; and establishing a prediction formula. Firstly, an independent component analysis (ICA) is applied to median-plane HRTFs from multiple subjects to obtain independent components and subject-dependent weight coefficients. Then, a factor analysis is used to select key anthropometric parameters relevant to HRTFs. Finally, a regression formula that connects ICA weight coefficients to key anthropometric parameters is established by a multiple linear regression. Further, the effectiveness of the proposed hybrid algorithm is verified by an objective evaluation via spectral distortion and a subjective localization experiment. The results show that, when compared with generic Knowles Electronics Manikin for Acoustic Research (KEMAR) HRTFs, the spectral characteristics of the predicted HRTFs are closer to those of the individualized HRTFs. Moreover, the predicted HRTFs can alleviate front-back and up-down confusion and improve the accuracy of localization for most subjects

    In-medium Properties of Θ+\Theta^{+} as a Kπ\piN structure in Relativistic Mean Field Theory

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    The properties of nuclear matter are discussed with the relativistic mean-field theory (RMF).Then, we use two models in studying the in-medium properties of Θ+\Theta^+: one is the point-like Θ\Theta^* in the usual RMF and the other is a Kπ\piN structure for the pentaquark. It is found that the in-medium properties of Θ+\Theta^+ are dramatically modified by its internal structure. The effective mass of Θ+\Theta^+ in medium is, at normal nuclear density, about 1030 MeV in the point-like model, while it is about 1120 MeV in the model of Kπ\piN pentaquark. The nuclear potential depth of Θ+\Theta^+ in the Kπ\piN model is approximately -37.5 MeV, much shallower than -90 MeV in the usual point-like RMF model.Comment: 8 pages, 5 figure