九大原子核セミナー

2012年6月5日(火) 16:30

講師：Pierre Descouvemont 氏 (Universite Libre de Bruxelles)
演題：
Scattering of exotic nuclei

場所：理学部 物理大学院講義室(理学部2号館2階2263室)

概要：
　Elastic scattering and breakup reactions represent efficient tools to investigate the structure of exotic nuclei. The main issue for theory is to determine their spectroscopic properties from the measured cross sections. The Continuum Discretized Coupled Channel (CDCC) method (at energies around the Coulomb barrier) and the eikonal method (at high energies) are widely used in reaction theories. Both approaches rely on projectile wave functions as accurate as possible.
　In this talk I present recent applications of the CDCC and eikonal methods with various types of projectile wave functions. Two-body (such as 11Be=10Be+n) and three-body (such as 11Li=9Li+n+n) examples are shown. In particular, recent data on the 11Be+64Zn elastic scattering are analysed in the CDCC formalism, and the inelastic process is discussed. I also present recent results, obtained with the eikonal method, on the 11Li breakup at high energies.

2012年5月25日(金) 16:30

講師：松本 琢磨 氏 (九州大学)

演題：
離散化チャネル結合法による不安定核分解反応の解析と核データ評価への応用

場所：理学部 物理大学院講義室(理学部2号館2階2263室)

概要：
離散化チャネル結合(CDCC)法は不安定核分解反応の解析に良く用いられ、最も信頼性のある方法の１つである。当初、CDCC法は3体反応系(入射核が2体に分解)の解析方法として提案され、現在では入射核が3体に分解する、標的核まで含めた4体系への拡張にも成功している。本講演では、これまで行ってきたCDCC法による不安定核分解反応の解析の結果について、さらにCDCC法の工学分野への応用の1つである、原子核反応データ評価について報告する。

2012年3月21日(水) 16:00

講師：Umesh Garg 氏 (University of Notre Dame/RIKEN)
演題：
Nuclear Incompressibility, the Asymmetry Term, and the MEM Effect

場所：理学部 物理大学院講義室(理学部2号館2階2263室)

概要：
The Nuclear Incompressibility parameter is one of three important components characterizing the nuclear equation of state. It has crucial bearing on diverse nuclear and astrophysical phenomena, including radii of neutron stars, strength of supernova collapse, emission of neutrinos in supernova explosions, and collective flow in medium- and high-energy nuclear collisions. In this talk I will review current status of the research on direct experimental determination of nuclear incompressibility via the compressional-mode giant resonances. In particular, recent measurements on a series of Sn and Cd isotopes have provided an "experimental" value for the asymmetry term of nuclear incompressibility. This term directly relates to properties of neutron stars. We also find that the GMR centroid energies of the in both Sn and Cd isotopes are significantly lower than the theoretical predictions, pointing to the role of superfluidity and the MEM (Mutual Enhancement of Magicity) Effect.

2012年3月19日(月) 16:00

講師：柏 浩司 氏 (理研BNL研究センター)
演題：虚数化学ポテンシャル及び強磁場系を用いたQCD相構造の研究

場所：理学部 物理大学院講義室(理学部2号館2階2263室)

概要：
　量子色力学の相構造を研究する上で格子QCDシミュレーションは非常に強力な手法である。しかし、有限の実数化学ポテンシャル領域では符号問題により格子QCD計算が破綻するため、現在のところ近似をもちいても温度が化学ポテンシャルを越える領域を調べることはできていない。そこで、有限実数化学ポテンシャルを調べるためQCDの有効模型が盛んに用いられているが、有効模型は不定性が非常に大きいため信頼できる相構造を得るには至っていない。つまり、”有効模型をどのように構築するのか”、”その際に使える条件をどのように得るのか”という事は有限温度・実数化学ポテンシャル領域でのQCD相構造を調べる上で非常に重要である。
　本発表では、近年注目を集めている”虚数化学ポテンシャル領域”と”空間一様な強磁場系”に着目し、模型構築に際してどのような制限を得ることが出きるかについて述べる予定である。特に、上記の両系はカイラル転移と非閉じ込め転移の非自明な相関を調べる事が出き
ると期待されている系である。

参考文献
K. Kashiwa, T. Hell, and W. Weise, Phys. Rev. D 84 (2011) 056010.
K. Kashiwa, Phys. Rev. D 83 (2011) 117901.

2012年2月16日(木) 16:00

講師：笹野 匡紀 氏 (理化学研究所)
演題：
Gamow-Teller transitions from 56Ni

場所：理学部 物理第三講義室(理学部2号館2階2249室)

概要：
The Gamow-Teller (GT) transition is the simplest excitation mode of atomic nuclei reflecting the interplay between spin and isospin degrees of freedom and, therefore, the transition strength is a key quantity for understanding the nuclear structures and interactions. Furthermore, electron-capture (EC) and beta-decay, which play important roles in type-II and typeIa supernovae, occur through the GT transitions. Thus, their strengths are also extensively studied to reliably estimate the weak-interactions rates. Experimentally, a powerful probe to study GT transitions has been provided by the charge-exchange reactions at intermediate energies such as the (p,n), (3He,t) rections. They can selectively excite the GT transitions in a wide excitation energy region. Until recently, however, such studies have been restricted to stable nuclei, or to a few low-lying states in a limited number of light unstable nuclei, because of difficulties in inverse-kinematics measurements with rare isotope (RI) beams. In this talk, we present a new experimental technique to measure the (p,n) reaction on any unstable nuclei and up to any excitation energy region, and its first application to study the GT transitions from 56Ni via the (p,n) reaction at 110 MeV/u in inverse kinematics. 56Ni is produced in large abundances during the pre-explosion phase of core-collapse supernovae and considered to be as one of the most important contributors to the change in the electron-to-baryon ratio in core-collapse supernovae. In addition, to study the GT transition in 56Ni serves as a stringent test of the effects of the N=Z=28 core not being inert on GT transitions for a large number of nearby nuclei in the Fe region. In this first study, a newly developed Low-Energy Neutron Detector Array (LENDA) was used in combination with the S800 spectrometer. To employ thus developed experimental method in conjunction with a high-intensity RI beam provided by RIKEN RI beam facility will provide a unique opportunity to study exotic properties of unstable nuclei near the proton/neutron drip lines through their GT transitions.