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Excited states in 17C were investigated through the measurement of β-delayed neutrons and γ rays emitted in the β decay of 17B. In the measurement, three negative-parity states and two inconclusive states were identified in 17C above the neutron threshold energy, and seven γ lines were identified in a β-delayed multiple neutron emission of the 17B β decay. From these transitions, the β-decay scheme of 17B was determined. In particular, a de-excitation 1766-keV γ line from the first excited state of 16C was observed in coincidence with the emitted β-delayed neutrons, and this changes the previously reported β-decay scheme of 17B and level structure of 17C. In the present work, the β-NMR technique is combined with the β-delayed particle measurements using a fragmentation-induced spin-polarized 17B beam. This new scheme allows us to determine the spin parity of β-decay feeding excited states based on the difference in the discrete β-decay asymmetry parameters, provided the states are connected through the Gamow-Teller transition. In this work, Iπ=1/2-, 3/2-, and (5/2-) are assigned to the observed states at Ex= 2.71(2), 3.93(2), and 4.05(2) MeV in 17C, respectively. [ABSTRACT FROM AUTHOR]

The excited states in the light nucleus 9Be are studied through β-delayed neutron decays from spin-polarized 9Lig.s.. The neutron transitions via 5Heg.s. from the 2.43-, 2.78-, 4.704-, 5.59-, and 7.94-MeV states in 9Be are observed for the first time, and the spins and parities (Iπ's) of the excited states in 9Be are assigned from β-n coincidences and measurements of the β-decay asymmetries. The spin parity, Iπ, of the 2.43-MeV state is assigned to be 5/2-, which is consistent with the reported value. The present results suggest that the Iπ values of the 2.78-, 4.704-, 5.59-, and 7.94-MeV states are 3/2-, 1/2-, 5/2-, and 3/2-, respectively, which are different from early reported values. However, shell-model calculations of the p shell are in overall good agreement with the present results, except for the Iπ values of the 2.78- and 4.704-MeV states. [ABSTRACT FROM AUTHOR]

Absolute cross sections for isotopically identified products formed in multinucleon transfer in the 136Xe+198Pt system at ~8 MeV/nucleon are reported. The isotopic distributions obtained using a large acceptance spectrometer demonstrated the production of the "hard-to-reach" neutron-rich isotopes for Z<78 around the N=126 shell closure far from stability. The main contribution to the formation of these exotic nuclei is shown to arise in collisions with a small kinetic energy dissipation. The present experimental finding corroborates for the first time recent predictions that multinucleon transfer reactions would be the optimum method to populate and characterize neutron-rich isotopes around N=126 which are crucial for understanding both astrophysically relevant processes and the evolution of "magic" numbers far from stability. [ABSTRACT FROM AUTHOR]

As the first step of systematic studies on neutron-rich Mg isotopes, the structure of 28Mg has been investigated by β-decay spectroscopy of spin-polarized 28Na at TRIUMF. Spin-parity assignments have been successfully performed for levels in 28Mg by taking advantage of the anisotropic β decay. Previous assignments for three levels were reconfirmed. New assignments were performed for four levels including a newly found 2+ level at 7.461 MeV. The experimental results were compared, on a level-by-level basis, with the shell-model calculation in the model space restricted to the sd shell. Overall good agreement between the experimental and theoretical results indicates dominance of the normal configurations in most of the 28Mg levels. High performance of the present method promises successful application to heavier Mg isotopes to elucidate the shell evolution in the region of the N = 20 island of inversion [ABSTRACT FROM AUTHOR]

Neutron single-particle states in the neutron-rich nucleus 35Si, which is located beside the N = 20 shell breaking nucleus 32Mg, were investigated through their isobaric analog resonances. The excitation function for 34Si+p elastic scattering was measured around 0d in the laboratory frame by the thick target inverse kinematics method with a 34Si beam around 5 MeV/nucleon and a thick polyethylene target. Eight resonances were successfully observed. Angular momenta and proton and total widths of the resonances were assigned using R-matrix analysis. With the help of information of the β decay study, six isobaric analog resonances were identified. Spectroscopic factors and spin-parities of the corresponding parent states in 35Si are presented. [ABSTRACT FROM AUTHOR]

Mass-separated 187Ta114 in a high-spin isomeric state has been produced for the first time by multinucleon transfer reactions, employing an argon gas-stopping cell and laser ionization. Internal γ rays revealed a T1/2 = 7.3 ± 0.9     s isomer at 1778 ± 1 keV, which decays through a rotational band with perturbations associated with the approach to a prolate-oblate shape transition. Model calculations show less influence from triaxiality compared to heavier elements in the same mass region. The isomer-decay reduced E2 hindrance factor fν = 27 ± 1 supports the interpretation that axial symmetry is approximately conserved. [ABSTRACT FROM AUTHOR]

We performed β and γ spectroscopy of 197g,198gOs and 198gIr, which were produced by multinucleon transfer reactions at the KEK Isotope Separation System (KISS). KISS was designed for the study of nuclear spectroscopy in the vicinity of N=126 for astrophysical interests. The β-decay half-life of 197gOs was revised to 91(8)s, while the half-life of 198gOs was measured for the first time and found to be 125(28)s. The β-decay schemes of 198gIr and 198gOs were partially established from this spectroscopic study. Based on presently suggested Iπ=(3/2or5/2)- and (0or1)- for 197gOs and 198gIr, respectively, the first-forbidden transitions of ν(3p3/2) or ν(2f5/2)→π(2d3/2) are suggested to be dominant. [ABSTRACT FROM AUTHOR]

The masses of the exotic isotopes 210-214Ac and 210-214Ra have been measured with a multireflection time-of-flight mass spectrograph. These isotopes were obtained in flight as fusion-evaporation products behind the gas-filled recoil ion separator GARIS-II at RIKEN. The new direct mass measurements serve as an independent and direct benchmark for existing α-γ spectroscopy data in this mass region. Further, new mass anchor points are set for U and Np nuclei close to the N=126 shell closure for a future benchmark of the Z=92 subshell for neutron-deficient heavy isotopes. Our mass results are in general in good agreement with the previously indirectly determined mass values. Together with the measurement data, reasons for possible mass ambiguities from decay-data links between ground states are discussed. [ABSTRACT FROM AUTHOR]

The magnetic dipole moment and mean-square charge radius of 199gPt (Iπ = 5/2-, t1/2 = 30.8 min) ground state and 199mPt (Eex = 424 keV, Iπ = (13/2)+, t1/2 = 13.6 s) isomeric state are evaluated for the first time from investigations of the hyperfine splitting of the λ1 = 248.792 nm transition by in-gas-cell laser ionization spectroscopy. Ground and isomeric states of neutron-rich 199Pt nucleus were produced by a multinucleon transfer reaction at the KEK Isotope Separation System (KISS), designed for the study of nuclear spectroscopy in the vicinity of N = 126. The measured magnetic dipole moments + 0.75 (8) μ N and - 0.57 (5) μ N are consistent with the systematics of those of nuclei with Iπ = 5/2 - and Iπ = 13/2+, respectively. [ABSTRACT FROM AUTHOR]

The 8Li (α, n) 11B reaction is regarded as the key reaction in the inhomogeneous big bang and in type-II supernova nucleosynthesis. Recently, the importance of this reaction to solving the 7Li problem, i.e., the inconsistency between the predicted and the observed primordial 7Li abundances, has also been noted. The most recent cross-section data published by our collaboration group in 2006 [H. Ishiyama et al., Phys. Lett. B 640, 82 (2006)] cover the 0.7-to 2.6-MeV energy region in the center-of-mass system. Here, we present additional data spanning the 0.45-to 1.8-MeV energy region. Thus, the predominant energy region for the big bang nucleosynthesis, corresponding to T9 = 1 (where T9 is a temperature unit equivalent to 109 K), is almost completely spanned by the previous [H. Ishiyama et al., Phys. Lett. B 640, 82 (2006)] and present results together. [ABSTRACT FROM AUTHOR]

Using a multireflection time-of-flight mass spectrograph located after a gas cell coupled with the gas-filled recoil ion separator GARIS-II, the masses of several a-decaying heavy nuclei were directly and precisely measured. The nuclei were produced via fusion-evaporation reactions and separated from projectilelike and targetlike particles using GARIS-II before being stopped in a helium-filled gas cell. Time-of-flight spectra for three isobar chains, 204Fr-204Rn-204At-204Po, 205Fr-205Rn-205At-205Po-205Bi, and 206Fr-206Rn-206At, were observed. Precision atomic mass values were determined for 204-206Fr, 204,205Rn, and 204,205At. Identifications of 205Bi, 204,205Po, 206Rn, and 206At were made with N≲10 detected ions, representing the next step toward use of mass spectrometry to identify exceedingly low-yield species such as superheavy elemention [ABSTRACT FROM AUTHOR]

The new isotope ^{241}U was synthesized and systematic atomic mass measurements of nineteen neutron-rich Pa-Pu isotopes were performed in the multinucleon transfer reactions of the ^{238}U+^{198}Pt system at the KISS facility. The present experimental results demonstrate the crucial role of the multinucleon transfer reactions for accessing unexplored neutron-rich actinide isotopes toward the N=152 shell gap in this region of nuclides.

The atomic masses of ^{55}Sc, ^{56,58}Ti, and ^{56-59}V have been determined using the high-precision multireflection time-of-flight technique. The radioisotopes have been produced at RIKEN's Radioactive Isotope Beam Factory (RIBF) and delivered to the novel designed gas cell and multireflection system, which has been recently commissioned downstream of the ZeroDegree spectrometer following the BigRIPS separator. For ^{56,58}Ti and ^{56-59}V, the mass uncertainties have been reduced down to the order of 10 keV, shedding new light on the N=34 shell effect in Ti and V isotopes by the first high-precision mass measurements of the critical species ^{58}Ti and ^{59}V. With the new precision achieved, we reveal the nonexistence of the N=34 empirical two-neutron shell gaps for Ti and V, and the enhanced energy gap above the occupied νp&#95;{3/2} orbit is identified as a feature unique to Ca. We perform new Monte Carlo shell model calculations including the νd&#95;{5/2} and νg&#95;{9/2} orbits and compare the results with conventional shell model calculations, which exclude the νg&#95;{9/2} and the νd&#95;{5/2} orbits. The comparison indicates that the shell gap reduction in Ti is related to a partial occupation of the higher orbitals for the outer two valence neutrons at N=34.

We report the first detection of the dark matter distribution around Lyman break galaxies (LBGs) at high redshift through the cosmic microwave background (CMB) lensing measurements with the public Planck PR3 κ map. The LBG sample consists of 1 473 106 objects with the median redshift of z∼4 that are identified in a total area of 305  deg^{2} observed by the Hyper Suprime-Cam Strategic Survey Program survey. After careful investigations of systematic uncertainties, such as contamination from foreground galaxies and cosmic infrared background, we obtain the significant detection of the CMB lensing signal at 5.1σ that is dominated by 2-halo term signals of the LBGs. Fitting a simple model consisting of the Navarro-Frenk-White profile and the linear-bias model, we obtain the typical halo mass of M&#95;{h}=2.9&#95;{-2.5}^{+9.5}×10^{11}  h^{-1} M&#95;{⊙}. Combining the CMB lensing and galaxy-galaxy clustering signals on the large scales, we demonstrate the first cosmological analysis at z∼4 that constrains (Ω&#95;{m0},σ&#95;{8}). We find that our constraint on σ&#95;{8} is roughly consistent with the Planck cosmology, while this σ&#95;{8} constraint is lower than the Planck cosmology over the 1σ level. This study opens up a new window for constraining cosmological parameters at high redshift by the combination of CMB and high-z galaxies, as well as studying the interplay between galaxy evolution and large-scale structure at such high redshift, by upcoming CMB and optical and near-infrared imaging surveys.

We measure the gravitational lensing shear signal around dark matter halos hosting constant mass galaxies using light sources at z∼1 (background galaxies) and at the surface of last scattering at z∼1100 (the cosmic microwave background). The galaxy shear measurement uses data from the CFHTLenS survey, and the microwave background shear measurement uses data from the Planck satellite. The ratio of shears from these cross-correlations provides a purely geometric distance measurement across the longest possible cosmological lever arm. This is because the matter distribution around the halos, including uncertainties in galaxy bias and systematic errors such as miscentering, cancels in the ratio for halos in thin redshift slices. We measure this distance ratio in three different redshift slices of the constant mass (CMASS) sample and combine them to obtain a 17% measurement of the distance ratio, r=0.390&#95;{-0.062}^{+0.070}, at an effective redshift of z=0.53. This is consistent with the predicted ratio from the Planck best-fit cold dark matter model with a cosmological constant cosmology of r=0.419.

We present significant evidence of halo assembly bias for SDSS redMaPPer galaxy clusters in the redshift range [0.1, 0.33]. By dividing the 8,648 clusters into two subsamples based on the average member galaxy separation from the cluster center, we first show that the two subsamples have very similar halo mass of M&#95;{200m}≃1.9×10^{14}  h^{-1}M&#95;{⊙} based on the weak lensing signals at small radii R≲10  h^{-1}Mpc. However, their halo bias inferred from both the large-scale weak lensing and the projected autocorrelation functions differs by a factor of ∼1.5, which is a signature of assembly bias. The same bias hypothesis for the two subsamples is excluded at 2.5σ in the weak lensing and 4.4σ in the autocorrelation data, respectively. This result could bring a significant impact on both galaxy evolution and precision cosmology.