Widths of the isobaric analog state of 208Pb

Both escape and spreading widths are evaluated microscopically in a consistent framework for the isobaric analog of the ²⁰⁸Pb ground state. A TDA Green function is obtained within the space of discretized J = 0⁺ proton-particle neutron-hole configurations using the Skyrme interaction. Couplings of these configurations with continuum and more complicated configurations are included into TDA matrix elements with a form of energy dependent terms. The energy and the widths of the isobaric analog resonance are obtained as a result of the matrix diagonalization. Comparison is made of the results with the former theoretical calculations as well as experimental data.     

Discovery of a narrow resonance state of the system K S K S at mass 1520 MeV

Data are presented which indicate the existence of a previously unknown narrow resonance near mass 1520 MeV, discovered while analyzing the system K _S K _S . The data were obtained at ITEP using the 6-m magnetic spectrometer in a beam of 40-GeV negative particles. The resonance is observed in π⁻ p and K ⁻ p interactions with a total statistical confidence of not less than 5 standard deviations. The width of this state is comparable to the mass resolution of the spectrometer (∼5 MeV). The mass is 1521.5±2.5 MeV. Estimates of the product σ·BR (K _S K _S ) give ∼5.0 nb in π⁻ p interactions and ∼250 nb in K ⁻ p interactions. From the fact that the production cross section of this resonance in the K ⁻ beam is approximately 50 times greater than the production cross section in the π⁻ beam, it can be concluded that this new state belongs to a system of mesons with hidden strangeness. Pis’ma Zh. éksp. Teor. Fiz. 70, No. 4, 242–246 (25 August 1999)     

The lifetime of the 5.14 MeV state in22Ne

Using the delayed coincidence method and the reaction¹⁹F(α, pγ)²²Ne at 10.80 MeV alpha energy, the lifetime of the 5.14 MeV state in²²Ne is determined to beτ=0.84 nsec±10%.     

Spin assignment of the 8.555 MeV state in28Si

Angular correlations between the gamma rays following the decay of the 8.555 MeV state in²⁸Si, known to have natural parity, were measured. The spin assignment of this state, found in this experiment, isJ ^π=6⁺. Energy sequence of the lowestJ ^π=2⁺, 4⁺ and 6⁺ states in²⁸Si compares well with the energy sequence of the ground state rotational bands in²⁰Ne and²⁴Mg.     

High-spin states in the A= 39 mirror nuclei 39Ca and 39K

High-spin states of the mass A= 39 mirror pair ³⁹K and ³⁹Ca were investigated via the fusion-evaporation reaction ²⁸Si +¹⁶O at 125 MeV beam energy. The Gammasphere array in conjunction with the 4π charged-particle detector array Microball and neutron detectors was used to detect γ rays in coincidence with evaporated light particles. The results of the first high-spin study of the T _z=−1/2 nucleus ³⁹Ca are discussed in terms of mirror symmetry and compared to spherical shell-model calculations in the 1d _3/2–; 1f _7/2 configuration space. Received: 18 August 1999     

Observation of a new resonance at 2000 MeV in the K S K S system

This article continues a series of publications devoted to previously unknown narrow resonances in the K _S K _S system that are observed in experimental data coming from the 6-m spectrometer of the Institute of Theoretical and Experimental Physics (ITEP, Moscow). The experimental data on the production of K _S pairs were obtained in π ^? p interactions at 40 GeV by using a neutral trigger. In the K _S K _S system, a maximum of width not exceeding 15 MeV is observed at a mass of about 2000 MeV, the statistical significance of this maximum being not less than five standard deviations. With a high degree of reliability, the spin-parity of this structure is J ^P = 4⁺. The observed phenomenon may be interpreted as a resonance whose parameters are equal to the above values.     

Resonance behavior of a K S K S system near the mass 1775 MeV

The preliminary results of an investigation of a system of two K _S mesons in the mass interval 1600–1950 MeV are reported. The events were obtained on a 6-m magnetic spark spectrometer at ITEP in π ⁻ p interactions at 40 GeV, using a neutral trigger which suppressed both charged particles and γ rays. A peak of width ≃30 MeV with statistical significance not lower than six standard deviations is observed with momentum transfer selection |tu|0.23 GeV² near the mass 1775 MeV of the K _S K _S system. The observed phenomena can be interpreted as the existence of one resonance with the indicated parameters, or two narrower resonances. In the latter case, their masses are 1768±1.5 and 1787±1.5 MeV. The widths of these states are comparable to the mass resolution of the spectrometer (∼5 MeV). Estimates of the product σ ⋅BR(K _S K _S ) give ∼1.5 and 2.5 nb, respectively, for the first and second states. Pis’ma Zh. éksp. Teor. Fiz. 68, No. 10, 727–731 (25 November 1998)     

Charge state distributions for 0.1–1.0 MeV Ne + Ne collisions using K x-ray measurements

High resolution measurements of K X-ray intensities are combined with total X-ray production cross sections and charge-state dependent fluorescence yields to obtain production cross sections for ions having one K and multiple L-shell vacancies. Deduced charge state distributions are compared with those determined from inelastic scattering studies and are used to set limits on the probability of having an electron in an excited state at the time of X-ray emission.     

Mixing of the giant magnetic dipole state with the 1+ state in 88Sr at 3.49 MeV

The ground state magnetic dipole transition width from the 1⁺ state in ⁸⁸Sr at 3.49 MeV is calculated using a reasonable wave function for the ground state and a wave function for the 1⁺ state calculated by diagonalizing one particle-one hole shell model 1⁺ states starting with a basis of reasonable dimensions. The calculated value of the width is 0.17 eV. The measured value is 0.15 ± 0.024 eV.     

Radiation from 39 and 45 MeV electrons channeled in Lithium Niobate

Abstract

Channeling radiation from 39 and 45 MeV electrons channeled along the <0001> axis, the (0110) plane and the (1210) plane of a 30 μm thick LiNbO ₃ crystal has been measured. Calculations of the planar crystal potentials were performed by means of the many-beam formalism. Good agreement between theory and experiment is obtained for the planar channeling radiation. Associated with channeling additional radiation lines have been observed, which may be explained by a periodic perturbation of the continuum potential.     

Determination of the cluster spectroscopic factor of the 10.3 MeV state in 12Be

From an inelastic excitation and breakup experiment with a ¹²Be beam at 29 MeV/u, a large ⁴He+⁸He cluster decay width of 1.1(2) MeV is determined for a state at an excitation energy of 10.3 MeV and with a spin parity of 0+. By using the R-matrix analysis, a cluster spectroscopic factor of 0.53(10) is extracted from the cluster partial width, providing a strong support for the clustering structure in ¹²Be. A specially designed zero-degree telescope played an essential role in the present experiment and has been demonstrated to be a promising tool in future studies of the molecular-like resonances near the cluster separation threshold.     

Pionic Fusion Study of the halo analogue state6Li

The isobaric analogue state of the ground state of the halo nucleus⁶He,⁶Li* has been studied in a pionic fusion experiment at the CELSIUS storage ring facility in Uppsala, Sweden. This was the first of two proposed experiments with the aim to study the high momentum part of the wave functions of the halo nuclei⁶He and⁶Li (0⁺, T=1). The Li nuclei were produced in inverse kinematics reactions with alpha particles incident on a deuterium cluster jet target. The⁶Li ions were detected in a zero-degree spectrometer situated in the fourth quadrant of the CELSIUS ring. The measurement was done for three different beam energies corresponding to 5.4, 2.2 and 1.5 MeV above threshold in the c.m. The cross-sections slowly increase with beam energy from 95 nb at the lowest energy to about 250 nb at 5.4 MeV above threshold.     

Electroexcitation of the first excited state in K

Electroexcitation of the first excited state in ³⁹K has been studied in the momentum transfer region of 0.8–2.5 fm⁻¹. Separation of the longitudinal and transverse form-factor components has been obtained. The longitudinal form factor has been analyzed model-independently. A B (M1) value for this l-forbidden transition was also obtained. Presently available theoretical predictions are unable to reproduce the B(M1) value or the transverse form-factor data.     

The lifetime of the 3.74 MeV (3) state of Ca

The mean life of the 3.74 MeV (3⁻) excited state of ⁴⁰Ca has been directly measured by a particle-gamma delayed coincidence technique. A mean life τ = 59 ± 5 ps was obtained, corresponding to a transition strength B(E3) = 31 ± 3 W.u.     

Widths of the Hall Conductance Plateaus

We study the charge transport of the noninteracting electron gas in a two-dimensional quantum Hall system with Anderson-type impurities at zero temperature. We prove that there exist localized states of the bulk order in the disordered-broadened Landau bands whose energies are smaller than a certain value determined by the strength of the uniform magnetic field. We also prove that, when the Fermi level lies in the localization regime, the Hall conductance is quantized to the desired integer and shows the plateau of the bulk order for varying the filling factor of the electrons rather than the Fermi level.     

Search for a light neutral particle in the decay of the 3.68 MeV state in C

A search is made for a short lived neutral particle, ø, in the decay of the 3.68 MeV (3/2^-) state in ¹³C. No evidence for such a particle with a rest mass in the region of 1.7–2.0 MeV/c² is found with a limit on the branching ratio Γ _ø/Γ_γ7×10 ⁻⁵. An upper limit of 10⁻⁶ is placed for the coupling of such a particle to proton/neutron.