Exotic Behaviour of Angular Dispersion of Weakly Bound Nucleus ^17F at Small Angles

The differential cross sections of ^17F and ^17O elastic scattering products on ^208Pb have been measured at the Radioactive Ion Beam Line at Lanzhou （RIBLL）. Two angular dispersion plots of In（ dσ/ dθ ） versus 02 are obtained from the angular distribution of the elastic scattering differential cross sections. The angular dispersion plot exhibits a clear turning point for ^17F in the range of small scattering angles 6°-2° due to its exotic structure, but for ^17O, the turning point is not observed in the same angular range. The experimental results have been compared with previous data of other groups. Systematical analysis on the available data supports the above conclusion that there is an exotic behaviour of the angular dispersion plot of weakly bound nuclei with halo or skin structure as compared with that of the ordinary nuclei near stable line. Therefore the turning point of the angular dispersion plot appears at small angle for weakly bound nuclei with halo or skin structure, and can be used as a new probe to investigate the halo and skin phenomena of weakly bound nuclei.     

Bremsstrahlung neutrino energy loss for ^24Mg, ^28Si, ^32S, ^40Ca, ^56Fe in strong electron screening

Based on Weinberg-Salam theory the bremsstrahlung neutrino energy loss for nuclei ^24Mg, ^28Si,^32S, ^40Ca and ^56Fe are investigated in strong electron screening. Our results are compared with those of Dicus＇ and show that the latter are higher by 2 orders of magnitude in the density-temperature region of 10^8 g/cm^3 ≤p/μe ≤ 10^11 g/cm^3 and 2.5≤ T9≤ 4.5. On the other hand, the factor C shows that the maximum differences are 99.16%, 99.13%, 99.12%, 99.055%, 99.040% corresponding to the nuclei ^24Mg, ^28Si, ^32S, ^40Ca and ^56Fe.     

^5He Emission in Neutron-Induced ^10B Reactions

In n ＋^10B reactions, ^5He cluster emission has been discussed with the updated level scheme and the new optical model parameters. In this paper the reaction channels related to ^5He emission are listed in detail. By using the new reaction model for light nuclei, the double-differential cross sections of total outgoing neutrons for n ＋ ^10 B reactions at En= 14.2 MeV have been calculated, and the results agree fairly well with the measurements. Particularly, in the energy-angular spectra the contribution from the 5He-emission to the total outgoing neutron double-differential cross sections has also been analyzed, and the partial energy-angular spectra of 60° at En= 14.2 MeV have been given. The calculated results indicate that once the 5He emission is taken into account, the fitting with the double-differential measurements of total outgoing neutrons at the low energy region could be improved. Therefore, to consider the ^5He emission properly in the reaction processes of light nuclei is necessary.     

Effect of Tensor Force on the Halo Structure of ^29Ne and ^31Ne

The structure of Ne isotopes has been investigated by using deformed Skyrme-Hartree-Fock （SHF） method and BCS approximation. Especially the effect of tensor force on the halo structure of 29Ne and 31Ne is discussed. To this end, the tensor contributions are considered to the energy density function and the single particle potential in SHF theory. For comparison, four Skyrme interactions are used： SLy5 and SGII without tensor force, and SLy5＋T and SGII＋ T with tensor force. The results indicate that the inclusion of tensor force shows a more pronounced halo structure for 31Ne.     

Measurement of the total reaction cross section for the mirror nuclei ^12N and ^12B

The mirror nuclei ^12N and ^12B are separated by the Radioactive Ion Beam Line in Lanzhou （RIBLL） at HIRFL from the breakup of 78.6 MeV/u 14N on a Be target. The total reaction cross-sections of ^12N at 34.9 MeV/u and ^12B at 54.4 MeV/u on a Si target have been measured by using the transmission method. Assuming ^12N consists of a ^11C core plus one halo proton, the excitation function of ^12N and ^12B on a Si target and a C target were calculated with the Glanber model. It can fit the experimental data very well. The characteristic halo structure for ^12N was found with a large diffusion of the protons density distribution.     

Measurement of Gamma-Rays from 11ΛB and 12ΛC

From the ^12 C（π^＋,K^＋）^12 AC reaction the γ -rays of 261.6±0.24 ke V（7/2^＋ →5/2^＋）and 1481.7±0.7 ke V（1/2^＋ →5/2^＋） of ^11 A B,and 2667.3±2.8 keV（1^- 2 → 2^- 1）of ^12 A C hypernuclei have been identified using a large germanium detector array Hyperball2 at K6 beam line of KEK. The observed energies of the transitions 1481.7keV and 261.6 keV are significantly different from the values predicted by the shell model using the △ and SN parameters determined from the ^7 △ Li data.     

Determination of the absolute microwave frequency of laser-cooled ^{171}\hbox {Yb}^+

\(^{171}\hbox {Yb}^+\) ions confined within a linear quadrupole trap were laser cooled to below 1 K. The microwave frequency of the hyperfine splitting of the ground state was continuously measured over 6 h. Frequency was corrected by evaluating the systematic shifts in each clock measurement. The absolute microwave frequency was determined as 12 642 812 118.468 2(4) Hz, in strong agreement with previously reported measurements.     

A new determination of the capture ratior_c = \frac{{\sum ^ - p \to \sum ^0 n}}{{(\sum ^ - p \to \sum ^0 n) + (\sum ^ - p \to \Lambda ^0 n)}}, the Λ0-lifetime and the ∑−-Λ0 mass difference

The two∑ ^? reactions at rest∑ ^? p→Λ ⁰ n and∑ ^? p→Λ ⁰ n have been studied in order to determine the capture ratio $$r_c = \frac{{\sum ^ - p \to \sum ^0 n}}{{(\sum ^ - p \to \sum ^0 n) + (\sum ^ - p \to \Lambda ^0 n)}}$$ , theΛ ⁰-lifetime and the∑ ^?-Λ ⁰ mass difference. The following results were obtained: $$\begin{gathered} rc = 0.474 \pm 0.016 \hfill \\ \tau _{\Lambda ^0 } = (2.47 \pm 0.08) \times 10^{ - 10} \sec \hfill \\ M_{\sum ^ - } - M_{\sum ^0 } = 81.64 \pm 0.09{{MeV} \mathord{\left/ {\vphantom {{MeV} {c^2 }}} \right. \kern-\nulldelimiterspace} {c^2 }} \hfill \\ \end{gathered} $$ The∑ ^?-mass was determined from the range of the stopping∑ ^?-hyperons,M _∑} =1197.19±0.32 MeV/c ².     

Determination of Astrophysical 13N（p,γ）^14O S-factors from the Asymptotic Normalization Coefficient of ^14C→^13C ＋ n

The angular distribution of the ^13C（d,p）^14C reaction is reanalysed using the Johnson-Soper approach. The squared asymptotic normalization coefficient （ANC） of virtual decay ^14 C →^13 C^14＋ n is then derived to be 21.4±5.0 fm^-1. The squared ANC and spectroscopic factor （SF） of ^14O→^13N ＋p are extracted to be 30.4± 7.1 fm^-1 and 1.94 ± 0.45, respectively. The astrophysical S-factors and reaction rates of ^13N（p, γ）140 are determined from the ANC of ^14O → ^13N ＋ P using the R-matrix approach.     

The masses of the 0^{++} and 0^{-+} light-quark hybrids using QCD sum rules

We calculate the masses of the light-quark hybrid mesons with the quantum numbers and by using the QCD sum rules. Two kinds of interpolated currents with the same quantum numbers are employed. We find that approximately equal masses are predicted for the hybrid state using the different currents, and different masses are obtained for the hybrid state using the different currents. The prediction depends on the interaction between the gluon and the quarks in the low-lying hybrid mesons. The mixing effect on the mass of the light-quark hybrid mesons through the low-energy theorem has also been examined, and it is found that this mixing shifts the masses of the hybrid mesons and the glueball a little. Received: 17 July 1998 / Revised version: 11 September 1998 / Published online: 15 April 1999     

Measurement of the Cross Section for the Process $${e^{+}e^{-}}{\to}{\omega\pi}^{{0}}{\to}{\pi}^{{+}}{\pi}^{{-}}{\pi}^{{0}}{\pi}^{{0}}$$ with the SND Detector

Physics of Atomic Nuclei - The process $$e^{+}e^{-}\to\omega\pi^{0}\to\pi^{+}\pi^{-}\pi^{0}\pi^{0}$$ was studied in the energy range between 1 and 2 GeV to the best precision in the world. The data...     

Results of the Further Analysis of Data from the Tien Shan Array in the Energy Spectrum of Primary Cosmic Rays in the Energy Range of $${2\times 10^{13}{-}3\times 10^{17}}$$ eV

Physics of Atomic Nuclei - The energy spectrum of primary cosmic rays at energies between 2 $$\times 10^{13}$$ and 3 $$\times 10^{17}$$ eV is presented according to data from the Tien Shan array on...     

Determination of Atomic Number Densities of ^87Rb and ^3He Based on Absorption Spectroscopy

The atomic number densities of ^87 Rb vapor and surrounding gas 3He in a sealed cubic cell were measured by sweeping the absorption line and fitting the experimental data with a Lorentzian profile. The absorption was carried out around the D1 transition at different temperatures. We compare our results for the number density for^87 Rb with the previous methods and calculate the fractional error to be less than 5% as well as the error for ^3He between this work and the density obtained from the filling procedure to be no more than 4.2% at 370K. In addition, we discuss the factors that contribute to the error, among which the cell temperature plays the most important role.