Gamma-ray spectroscopy of hypernuclei: Recent results and future plans

A series of hypernuclear γ-ray spectroscopy experiments using a germanium detector array, Hyperball, have accumulated precise data on various p-shell Λ hypernuclei. Recently, ¹²_ΛC and ¹¹_ΛB were studied at KEK using the (π⁺,K⁺γ) reaction, and a transition from a directly-populated spin-flip state, ¹⁶_ΛO(2⁻), was observed in BNL E930 data. It is discussed whether the spin-dependent ΛN interaction parameters determined from previous experiments can consistently explain other γ spectroscopy data. At the J-PARC facility, further hypernuclear γ-ray spectroscopy experiments are planned, particularly to measure the g factor of a Λ in a nucleus from a spin-flip B(M1) value and to investigate the ΛN interaction more in detail.     

Modelling interstellar extinction and polarization with spheroidal grains

We calculate the wavelength dependence of the ratio of the linear polarization degree to extinction (polarizing efficiency) P(λ)/A(λ) from the ultraviolet to near-infrared. The prolate and oblate particles with aspect ratios from a/b=1.1 up to 10 are assumed to be rotating and partially aligned with the mechanism of paramagnetic relaxation (Davis–Greenstein). Size/shape/orientation effects are analyzed. It is found that the wavelength dependence of P(λ)/A(λ) is mainly determined by the particle composition and size whereas the values of P(λ)/A(λ) depend on the particle shape, degree and direction of alignment.     

Calibration of the Makrofol–DE nuclear track detector using relativistic lead ions

We present the calibration of the Makrofol–DE nuclear track detector (NTD) using Pb-ions of 158 GeV/amu. Improvements in the post-etched surfaces, reduction in the surface background of the Makrofol–DE NTDs and high-contrast tracks were achieved with the appropriate addition of ethyl alcohol in KOH aqueous solutions. The calibration of Makrofol–DE has shown for the first time all the peaks arising due to nuclear fragments with Z52. The measurement of the cone heights shows well-separated individual peaks for Z/β=59–82 and 83 (charge pickup).     

奇Z超重核的禁戒α衰变(英文)

采用密度依赖的结团模型研究了奇Z 超重核的禁戒α衰变, 粒子与子核之间的微观核势通过双折叠模型对M3Y 核子-核子相互作用势以及 粒子与子核的密度积分给出。 粒子与子核之间的库仑相互作用也通过 粒子与子核的电荷密度积分给出。计算发现,由于非零角动量带来的禁戒效应和小的α粒子预形成几率,奇Z 超重核的α衰变寿命会明显变长。We investigate the α-transition of odd-Z superheavy nuclei by the density-dependent cluster model (DDCM). The microscopic nuclear potential between the -particle and the daughter nucleus is evaluated numerically from the double-folding model with the standard M3Y nucleon-nucleon interaction. The Coulomb potential is also obtained from the double-folding integral of the proton-proton Coulomb interaction with the charge density distributions of α-particle and daughter nucleus. From our calculations, enhanced stability againstα-decays is found for the odd-Z superheavy nuclei due to the hindrance effect of non-zero angular momentum and the small preformation factor of the -particle.     

hypernuclei based on the ESC04 model

Structures of S=−2 many-body states (double-Λ and Ξ hypernuclei) are investigated on the basis of G-matrix interactions derived from the recently-developed extended-soft-core model (ESC04d). ΛΛ–ΞN mixing effects in ⁶_ΛΛHe, ⁵_ΛΛH and ⁵_ΛΛHe are investigated with use of three-body models. Possible Ξ hypernuclei are investigated systematically with Ξ-core folding potentials derived from ΞN G-matrix interactions. A four-body narrow Ξ⁰–Ξ⁻ mixed state, specific to ESC04d, is discussed.     

A point source solution for unidirectional flow of a viscoelastic fluid

A Fourier point source solution modelling the effect of an impulse on a viscoelastic fluid of second-grade is investigated. By examining the second-moment of a Fourier point source solution we show that for Dt1, where D=ν/ for ν the kinematic viscosity, a viscoelastic parameter and t the time; the fluid undergoes superdiffusion indicating the dominance of the fluids viscoelastic properties. For Dt1 the fluid undergoes classical diffusion indicating that the viscous properties of the fluid are dominating.     

Hypernuclear spectroscopy program at JLab Hall C

Hypernuclear production by the (e,e^′K⁺) reaction has unique advantages in hypernuclear spectroscopy of the S=−1 regime. The second-generation spectroscopy experiment on ¹²C, ⁷Li and ²⁸Si targets has been recently carried out at JLab Hall C with a new experimental configuration (Tilt method) and also using a new high-resolution kaon spectrometer (HKS). The experiment is described and preliminary results are presented together with the empasis of significance of the (e,e^′K⁺) reaction for Λ hypernuclear spectroscopy and its future prospects.     

Higher impurity AdS/CFT correspondence in the near-BMN limit

The pp-wave/BMN limit of the AdS/CFT correspondence has exposed the Maldacena conjecture to a new regimen of direct tests. In one line of pursuit, finite-radius curvature corrections to the Penrose limit (which appear in inverse powers of the string angular momentum J) have been found to induce a complicated system of interaction perturbations to string theory on the pp-wave; these have been successfully matched to corresponding corrections to the BMN dimensions of N=4 super-Yang–Mills (SYM) operators to two loops in the 't Hooft coupling λ. This result is tempered by a well-established breakdown in the correspondence at three loops. Notwithstanding the third-order mismatch, we proceed with this line of investigation by subjecting the string and gauge theories to new and significantly more rigorous tests. Specifically, we extend our earlier results at O(1/J) in the curvature expansion to include string states and SYM operators with three worldsheet or R-charge impurities. In accordance with the two-impurity problem, we find a perfect and intricate agreement between both sides of the correspondence to two-loop order in λ and, once again, the string and gauge theory predictions fail to agree at third order.     

The third-order optical nonlinearity of The pyrochlore phase 0.7Pb(Mg1/3Nb2/3)O3–0.3PbTiO3 thin film on quartz

The xPb(Mg_1/3Nb_2/3)O₃–(1−x)PbTiO₃ (PMNT) (with x=0.7) thin film is prepared on quartz substrates prepared using a sol–gel process. The PMNT thin film has a well-crystallized pyrochlore phase structure. The sign and magnitude of both real and imaginary parts of third-order nonlinear susceptibility χ⁽³⁾ of the thin film have been determined by the Z-scan technique performed at 800 nm with a femtosecond laser. The nonlinear refraction index coefficient γ, the nonlinear absorption coefficient β of the thin film are 1.37×10⁻¹² cm²/W and −6.73×10⁻⁸ m/W, respectively. The real and imaginary part of the third-order nonlinear susceptibility of the film are 1.06×10⁻¹⁷ and −1.65×10⁻¹⁹ m²/V², respectively. The results suggested that the nonlinearity is dominated by the refractive for the film.     

The antikaon–nucleus interaction and alternative views to deeply bound antikaonic nuclear systems

We present an overview of the latest theoretical studies on the antikaon properties in the nuclear medium, in connection with the recent experimental claims of very deeply bound antikaon nuclear states. We argue that proper many-body formulations using modern realistic antikaon–nucleon interactions are not able to generate such systems. Instead, a simple two-nucleon antikaon absorption mechanism where the remaining nucleus acts as spectator explains the enhancement observed in semi-inclusive proton momentum spectra, seen as a bump in the KEK PS-E549 experiment on a ⁴He target or as a peak in the FINUDA experiment on a ⁶Li target. This signal is clearly visible in another FINUDA experiment measuring the invariant mass of Λ-proton pairs after two-nucleon kaon absorption. We also show that another peak of this experiment, seen at lower invariant masses and interpreted as a bound K⁻pp state, is simply generated by the same two-nucleon absorption mechanism followed by final-state interactions of the produced particles with the residual nucleus. Our conclusion is that all the experimental claims for the formation of very deeply bound antikaonic nuclear systems receive an alternative explanation in terms of conventional nuclear processes.     

Measurements of decays into and

Based on a sample of 5.8×10⁷ J/ψ events taken with the BESII detector, the branching fractions of J/ψ→2(π⁺π⁻)η and J/ψ→3(π⁺π⁻)η are measured for the first time to be (2.26±0.08±0.27)×10⁻³ and (7.24±0.96±1.11)×10⁻⁴, respectively.     

Is the β phase maximal?

The current experimental determination of the absolute values of the CKM elements indicates that 2|V_ub/V_cbV_us|=(1−z), with z given by z=0.19±0.14. This fact implies that irrespective of the form of the quark Yukawa matrices, the measured value of the SM CP phase β is approximately the maximum allowed by the measured absolute values of the CKM elements. This is for , which implies =π/2. Alternatively, assuming that β is exactly maximal and using the experimental measurement sin(2β)=0.726±0.037, the phase γ is predicted to be γ=(π/2−β)=66.3°±1.7°. The maximality of β, if confirmed by near-future experiments, may give us some clues as to the origin of CP violation.     

On the behavior of spallation neutrons from extended Pb targets plus moderator: A comparison between SSNTD measurements and calculation

Thick Pb targets of different lengths were irradiated by 1 GeV protons at the Nuclotron accelerator of the High Energy Laboratory, JINR, Dubna. To favor transmutation via (n,γ) reactions a paraffin moderator is used. Solid-state nuclear track detectors (SSNTDs) measured neutron distribution. A comparison of experimental results with calculation on the moderator surface is given.     

Conditional observability

For a quantum Hamiltonian H=H(λ), the observability of the energies E may be robust (whenever all E are real at all λ) or, otherwise, conditional. Using a pseudo-Hermitian family of N-state chain models H=H^(N)(λ) we discuss some generic properties of conditionally observable spectra.     

Search for intermediate mass magnetic monopoles and nuclearites with the SLIM experiment

SLIM is a large area experiment (440 m²) installed at the Chacaltaya cosmic ray laboratory since 2001, and about 100 m² at Koksil, Himalaya, since 2003. It is devoted to the search for intermediate mass magnetic monopoles (10⁷–10¹³ GeV/c²) and nuclearites in the cosmic radiation using stacks of CR-39 and Makrofol nuclear track detectors. In four years of operation it will reach a sensitivity to a flux of about 10^-15 cm^-2 s^-1 sr^-1. We present the results of the calibration of CR-39 and Makrofol and the analysis of a first sample of the exposed detector.     

Correlation among electronic polarizability, optical basicity and interaction parameter of Bi2O3–B2O3 glasses

For optical basicity and electronic polarizability, the previous studies basically concentrate on the wavelength range of the visible light region. However, heavy metal oxides glasses have a reputation of being good materials for infrared region. In this study, new data of the average electronic polarizability of the oxide ion _O^2-, optical basicity Λ and Yamashita–Kurosawa's interaction parameter A of Bi₂O₃–B₂O₃ glasses have been calculated in a wavelength range from 404.66 to 1083.03 nm. The present investigation suggests that both _O^2- and Λ increase gradually with increasing wave number, and A decreases with increasing wave number. Furthermore, close correlations are studied among _O^2-, Λ, A and refractive index n in this paper. Particularly, it has been found that a quantitative relationship between electronic polarizability and optical basicity is observed in a wavelength range from 404.66 to 1083.03 nm. Our present study extends over a wide range of _O^2-, Λ and A values.     

Note on spin–orbit interactions in nuclei and hypernuclei

A detailed comparison is made between the spin–orbit interactions in Λ hypernuclei and ordinary nuclei. We argue that there are three major contributions to the spin–orbit interaction: (1) a short-range component involving scalar and vector mean fields; (2) a “wrong-sign” spin–orbit term generated by the pion exchange tensor force in second order; and (3) a three-body term induced by two-pion exchange with excitation of virtual Δ(1232)-isobars (à la Fujita–Miyazawa). For nucleons in nuclei the long-range pieces related to the pion-exchange dynamics tend to cancel, leaving room dominantly for spin–orbit mechanisms of short-range origin (parametrized, e.g., in terms of relativistic scalar and vector mean fields terms). In contrast, the absence of an analogous 2π-exchange three-body contribution for Λ hyperons in hypernuclei leads to an almost complete cancellation between the short-range (relativistic mean-field) component and the “wrong-sign” spin–orbit interaction generated by second order π-exchange with an intermediate Σ hyperon. These different balancing mechanisms between short- and long-range components are able to explain simultaneously the very strong spin–orbit interaction in ordinary nuclei and the remarkably weak spin–orbit splitting in Λ hypernuclei.     

Electronic and optical properties of BaTe, BaSe and BaS from first principles

Electronic and optical properties of barium chalcogenide compounds BaX (X=S, Se and Te) in NaCl crystal structure are calculated using the band structure results obtained through the full potential linearized augmented plane wave (FP-LAPW) method. The exchange correlation potential is treated by the generalized gradient approximation. The real and imaginary parts of the dielectric function ε(ω), the optical absorption coefficient I(ω), the reflectivity R(ω) and the energy loss function are calculated. The calculated results show good agreement with the available experimental results, particularly in the low-energy region of the spectra. Furthermore the interband transitions responsible for the structures seen in the spectra are specified. It is shown that the chalcogen p states and Ba 5d states play a major role in optical transitions as initial and final states, respectively. The effect of the spin–orbit coupling on the optical properties is also investigated and found to be significant, especially in high-energy regions.     

Peakon, compacton and loop excitations with periodic behavior in KdV type models related to Schrödinger system

In this Letter, the linear variable separation approach is successfully extended to (1+1)-dimensional Korteweg–de Vries (KdV) type models related to Schrödinger system. Some significant types of solitons such as compacton, peakon and loop solutions with periodic behavior are simultaneously derived from the (1+1)-dimensional soliton system by entrancing appropriate piecewise smooth functions and multivalued functions.     

XRD studies on the femtosecond laser ablated single-crystal germanium in air

Ultrashort laser ablation of single-crystal germanium has been performed in air with femtosecond laser pulses (150 fs, 1 kHz) of 810 nm in the laser fluence range of 0.7–35.4 J/cm². Ablation depth dependence on the laser fluence shows that there are two different processes, which are explained in terms of electronic heating process and the optical penetration one. Structure of ablated region is characterized by means of two different XRD techniques. With increasing the laser fluence higher than 10.2 J/cm², the laser-processed region of germanium exhibits poly-crystalline diffraction peaks in a wide-angle (θ/2θ) scan and a split of diffraction peak of (4 0 0) plane in the rocking curve, which are absent in the lower laser fluence. These observations could be explained in terms of structural changes induced by ultrashort laser irradiation at the higher laser fluence.