Quadrupole Moments of Neutron-Deficient 20,21^{20, 21}Na

The electric-quadrupole coupling constant of the ground states of the proton drip line nucleus $^{20}$Na($I^{\pi}$ = 2$^{+}$, $T_{1/2}$ = 447.9 ms) and the neutron-deficient nucleus $^{21}$Na($I^{\pi}$ = 3/2$^{+}$, $T_{1/2}$ = 22.49 s) in a hexagonal ZnO single crystal were precisely measured to be $|eqQ/h| = 690 \pm 12$ kHz and 939 $\pm$ 14 kHz, respectively, using the multi-frequency $\beta$-ray detecting nuclear magnetic resonance technique under presence of an electric-quadrupole interaction. A electric-quadrupole coupling constant of $^{27}$Na in the ZnO crystal was also measured to be $|eqQ/h| = 48.4 \pm 3.8$ kHz. The electric-quadrupole moments were extracted as $|Q(^{20}$Na)$|$ = 10.3 $\pm$ 0.8 $e$ fm$^2$ and $|Q(^{21}$Na)$|$ = 14.0 $\pm$ 1.1 $e$ fm$^2$, using the electric-coupling constant of $^{27}$Na and the known quadrupole moment of this nucleus as references. The present results are well explained by shell-model calculations in the full $sd$-shell model space.Comment: Accepted for publication in Physics Letters

Fast switching NMR system for measurements of ground-state quadrupole moments of short-lived nuclei

A beta-ray detecting nuclear quadrupole resonance system has been developed at NSCL/MSU to measure ground-state electric quadrupole moments of short-lived nuclei produced as fast rare isotope beams. This system enables quick and sequential application of multiple transition frequencies over a wide range. Fast switching between variable capacitors in resonance circuits ensures sufficient power delivery to the coil in the beta-ray detecting nuclear magnetic resonance technique. The fast switching technique enhances detection efficiency of resonance signals and is especially useful when the polarization and/or production rate of the nucleus of interest are small and when the nuclear spin is large

Test of the Conserved Vector Current Hypothesis by beta-ray Angular Distribution Measurement in the Mass-8 System

The beta-ray angular correlations for the spin alignments of 8Li and 8B have been observed in order to test the conserved vector current (CVC) hypothesis. The alignment correlation terms were combined with the known beta-alpha-angular correlation terms to determine all the matrix elements contributing to the correlation terms. The weak magnetism term, 7.5\pm0.2, deduced from the beta-ray correlation terms was consistent with the CVC prediction 7.3\pm0.2, deduced from the analog-gamma-decay measurement based on the CVC hypothesis. However, there was no consistent CVC prediction for the second-forbidden term associated with the weak vector current. The experimental value for the second-forbidden term was 1.0 \pm 0.3, while the CVC prediction was 0.1 \pm 0.4 or 2.1 \pm 0.5.Comment: 31 pages, 12 figures, Accepted for publication in Phys. Rev.

Proton Irradiation Experiment for the X-ray Charge-Coupled Devices of the Monitor of All-sky X-ray Image mission onboard the International Space Station: I. Experimental Setup and Measurement of the Charge Transfer Inefficiency

We have investigated the radiation damage effects on a CCD to be employed in the Japanese X-ray astronomy mission including the Monitor of All-sky X-ray Image (MAXI) onboard the International Space Station (ISS). Since low energy protons release their energy mainly at the charge transfer channel, resulting a decrease of the charge transfer efficiency, we thus focused on the low energy protons in our experiments. A 171 keV to 3.91 MeV proton beam was irradiated to a given device. We measured the degradation of the charge transfer inefficiency (CTI) as a function of incremental fluence. A 292 keV proton beam degraded the CTI most seriously. Taking into account the proton energy dependence of the CTI, we confirmed that the transfer channel has the lowest radiation tolerance. We have also developed the different device architectures to reduce the radiation damage in orbit. Among them, the ``notch'' CCD, in which the buried channel implant concentration is increased, resulting in a deeper potential well than outside, has three times higher radiation tolerance than that of the normal CCD. We then estimated the charge transfer inefficiency of the CCD in the orbit of ISS, considering the proton energy spectrum. The CTI value is estimated to be 1.1e-5 per each transfer after two years of mission life in the worse case analysis if the highest radiation-tolerant device is employed. This value is well within the acceptable limit and we have confirmed the high radiation-tolerance of CCDs for the MAXI mission.Comment: 17 pages, 2 table, 12 figures. Accepted for publication of Japanese Journal of Applied Physics. High resolution file is available from http://wwwxray.ess.sci.osaka-u.ac.jp/~miyata/paper/proton_cti.pd

Dipole and Quadrupole Moments of Mirror Nuclei 8B and 8li

Magnetic dipole and electric quadrupole moments of the mirror nuclei 8Li and 8B are analysed in the framework of the multiparticle shell model by using two approaches : i) the one-particle spectroscopic factors and ii) the one-particle fractional parentage coefficients. These two approaches are compared both each to other and with a microscopic multicluster model. The one-particle nucleon states are calculated taking into account the continuum by the method of the expansion of the Sturm - Liouville functions. The experimental magnetic and quadrupole moments of 8Li and 8Bare reproduced well by using fractional parentage coefficients technique. The root mean-square radii and the radial density distributions are obtained for these nuclei.Comment: 20 pages 1 figur

Dynamical Interpretation of the Nucleon-Nucleon Interaction and Exchange Currents in the Large NCN_C Limit

Expression of the nucleon-nucleon Interaction to order $1/N_C$ in terms of Fermi Invariants allows a dynamical interpretation of the interaction and leads to a consistent construction of the associated interaction currents to order $1/N_C$. The numerically significant components of 4 different modern realistic phenomenological interaction models are shown to admit very similar meson exchange interpretations in the large $N_C$ limit. Moreover the ratio of the volume integrals of the leading, next-to-leading and next-to-next leading order terms in these interaction models is roughly 300:5-10:0.1, which corresponds fairly well to the ratios of $1/N_C^2$ between the terms that would be suggested by the $1/N_C$ expansion if $N_C=3$. The $N_C$ dependence of the electromagnetic and axial interaction currents that are associated with these interaction components is derived and compared to that of the corresponding single nucleon currents.Comment: 29 pages, LateX, 11 figure

Effects of B-8 size on the low-energy Be7(p,gamma)B8 cross section

We calculate several "size-like" B-8 observables within the microscopic three-cluster model and study their potential constraints on the zero-energy astrophysical S_{17}(0) factor of the Be7(p,gamma)B8 reaction. We find within our three-cluster model that a simultaneous reproduction of the experimental data for the B-8 radius and quadrupole moment and of the B8-Li8 Coulomb displacement energy implies S_{17}(0)=(23-25) eVb.Comment: 8 pages with 1 figure. The original version with further details and more information are available at http://qmc.lanl.gov/~csot

Second Class Current in QCD Sum Rules

Induced tensor charge of the nucleon $g_T$, which originates from G-parity violation, is evaluated from QCD sum rules. We find that $g_T/g_A$ with $g_A$ being the axial charge is $-$0.0152 $\pm$ 0.0053 which is proportional to u-d quark mass difference. This result is small compared to preliminary analysis of the experiment, but is consistent with the estimate in the MIT bag model.Comment: 20 pages, latex, 7 figures appended as uu-encoded fil