Kaon interferometry in heavy-ion collisions at the CERN SPS

K⁺K⁺ and K^–K^– correlations from S+Pb collisions at 200 GeV/c per nucleon and K⁺K⁺ correlations from p+Pb collisions at 450 GeV/c per nucleon, are presented as measured by the focusing spectrometer of the NA44 experiment at CERN. Multidimensional fits are performed in order to characterize the kaon-emission volume, which is found to be smaller than the pion-emission volume.     

Two-kaon correlations in central Pb+Pb collisions at 158 a GeV/c

Two-particle interferometry of positive kaons is studied in Pb+Pb collisions at mean transverse momenta approximately 0.25 and 0.91 GeV/c. A three-dimensional analysis was applied to the lower p(T) data, while a two-dimensional analysis was used for the higher p(T) data. We find that the source-size parameters are consistent with the m(T) scaling curve observed in pion-correlation measurements in the same collisions, and that the duration time of kaon emission is consistent with zero within the experimental sensitivity.     

Characteristics improvement of HfO2/Ge gate stack structure by fluorine treatment of germanium surface

Chemical reactivity of fluorine molecule (F₂)-germanium (Ge) surface and dissociation of fluorine (F)-Ge bonding have been simulated by semi-empirical molecular orbital method theoretically, which shows that F on Ge surface is more stable compared to hydrogen. Ge MIS (metal insulator semiconductor) capacitor has been fabricated by using F₂-treated Ge(1 0 0) substrate and HfO₂ film deposited by photo-assisted MOCVD. Interface state density observed as a hump in the C-V curve of HfO₂/Ge gate stack and its C-V hysteresis were decreased by F₂-treatment of Ge surface. XPS (X-ray photoelectron spectroscopy) depth profiling reveals that interfacial layer between HfO₂ and Ge is sub-oxide layer (GeO_x or HfGeO_x), which is believed to be origin of interface state density.F was incorporated into interfacial layer easily by using F₂-treated Ge substrate. These results suggest that interface defect of HfO₂/Ge gate stack structure could be passivated by F effectively.     

Coherent transfer of light polarization to electron spins in a semiconductor

We demonstrate that the superposition of light polarization states is coherently transferred to electron spins in a semiconductor quantum well. By using time-resolved Kerr rotation, we observe the initial phase of Larmor precession of electron spins whose coherence is transferred from light. To break the electron-hole spin entanglement, we utilized the big discrepancy between the transverse g factors of electrons and light-holes. The result encourages us to make a quantum media converter between flying photon qubits and stationary electron-spin qubits in semiconductors.     

Relaxation structure analysis of Li inserted γ-Fe2O3

γ-Fe₂O₃ has a spinel structure with cation vacancy and is expected to perform as a favorable electrode material for secondary lithium-ion battery. When lithium is inserted electrochemically into γ-Fe₂O₃, prolonged potential change is observed after the insertion. In this study, we inserted various amount of Li into γ-Fe₂O₃ (x = 0.66, 1.1, 1.5 in terms of Li_XFe₂O₃), then made the circuit open, measured X-ray diffraction (XRD) patterns at various elapsed time, and analyzed the crystal structure change of γ-Fe₂O₃ with time by the Rietveld method. The X-ray Rietveld analysis revealed that the iron occupancy of 8a site decreased and that of 16c site increased with lithium insertion process and after lithium insertion, the iron occupancy of 8a site increased and that of 16c site decreased gradually with relaxation time. It is indicated that lithium prefer 8a site to occupy kinetically, on the other hand, prefer 16c site thermodynamically.     

Apparent diffusion coefficient of line scan diffusion image in normal prostate and prostate cancer—comparison with single-shot echo planner image

Purpose

This retrospective study was designed to evaluate the apparent diffusion coefficient (ADC) of line scan diffusion images (LSDI) in normal prostate and prostate cancer. Single-shot echo planner images (SS-EPI) were used for comparison.

Materials and Methods

Twenty prostate tumors were examined by conventional MRI in 14 patients prior to radical prostatectomy. All patients were examined with a 1.5-T MR imager (Signa CV/i ver. 9.1 GE Medical System Milwaukee, WI, USA). Diffusion-weighted MR imaging (DWI) using LSDI was performed with a pelvic phased-array coil, with b values of 5 and 800 s/mm². DWI using SS-EPI was performed with a body coil, with b values of 0 and 800 s/mm². The ADCs of each sequence for 14 normal prostate and 20 prostate cancers were histopathologically assessed. Signal-to-noise ratio (SNR) on DWI was estimated and compared for each sequence.

Results

The mean ADCs (±S.D.) of normal peripheral zones (PZ), transition zones (TZ) and cancer (in 10⁻³ mm²/s) that used LSDI were 1.42±0.12, 1.23±0.10 and 0.79±0.19, respectively. Those that used SS-EPI were 1.76±0.26, 1.38±0.20 and 1.05±0.27, respectively. Using unpaired t test (P<.05), we found a significant difference in each sequence between normal tissue (both PZ and TZ) and the cancer. Paired t test (P<.05) also registered a significant difference between LSDI and SS-EPI. Mean SNR for DWI using LSDI was 16.49±5.03, while the DWI using SS-EPI was 18.85±9.26. The difference between the SNR of each sequence was not statistically significant by paired t test.

Conclusion

We found that ADCs using LSDI and SS-EPI showed similar tendencies in the same patients. However, in all regions, LSDI ADCs had smaller standard deviations than SS-EPI ADCs.     

A case of Budd-Chiari syndrome: Gd-EOB-DTPA-enhanced MR findings

Budd-Chiari syndrome (BCS) is a rare disorder caused by the obstruction of hepatic venous outflow, leading to sinusoidal congestion, ischemic injury to liver cells and portal hypertension. Long-term survival largely depends on whether hepatocellular carcinoma occurs. A recently available liver-specific contrast medium, gadolinium-ethoxybenzyl-diethylenetriamine penta-acetic acid (Gd-EOB-DTPA), reportedly has high diagnostic capability for detection of malignant liver tumors. However, there has been no report of the sue of Gd-EOB-DTPA-enhanced magnetic resonance imaging (MRI) for BCS. We present a case of chronic BCS who underwent both gadopentetate dimeglumine (Gd-DTPA) and Gd-EOB-DTPA-enhanced MRI. Hepatic congestion and edema were seen as slightly hypointense areas on Gd-EOB-DTPA-enhanced hepatobiliary-phase images, although these areas were observed as slightly hyperintense on previously obtained Gd-DTPA-enhanced delayed-phase image. Reduced uptake of Gd-EOB-DTPA by hepatocytes in the region of congestion or edema may account for this difference, which should be recognized in image interpretations.     

Spectroscopic Measurement in 9He and 12Be

Spectroscopy for neutron-rich nuclei ⁹He and ¹²Be has been performed by means of heavy-ion double charge exchange (HIDCX) (¹⁸O, ¹⁸Ne) reaction on stable target nuclei ⁹Be and ¹²C, respectively. Several clear peaks in ¹²Be at low excitation energy region even above neutron separation energy have been observed in one-shot measurement, whereas no prominent signals of ⁹He have been observed owing to the small cross section. It is shown that the HIDCX reaction is a new powerful spectroscopic tool for study of unstable neutron-rich nuclei.     

Study of Strangeness Photoproduction on the Neutron in the Threshold Region

Photoproduction of the neutral kaon on the deuteron has been investigated at the Research Center for Electron Photon Science, Tohoku University. We constructed the Neutral Kaon Spectrometer-2 for the detection of charged particles from the decay of the neutral kaon and the hyperon. We obtained a momentum distribution of K ⁰ with the inclusive measurement. It was consistent with the previous measurement. The total cross section of γ + d → K ⁰ + Λ + p was estimated from the measured integral cross section of γ + d → Λ + X. The total cross section with respect to the photon energy was compared with the theoretical calculations. It favored the Saclay-Lyon A model calculation with the ratio of the neutral to charged coupling constants of the axial-vector meson, K ₁, as ~ ?1.5. The energy dependence and the magnitude of the total cross section were similar to the total cross section of γ + p → K ⁺ Λ.