九大原子核セミナー

九州大学の原子核理論と原子核実験の共同開催のセミナー

第950回九大原子核セミナー

2018年7月6日(金) 16:30〜18:00

講師: 福田 光順 氏 (大阪大学)
演題:核反応で探る原子核構造

場所:ウェスト1号館7階 物理セミナー室2 (W1-A-722室)

概要:
1980年代に谷畑さんらはバークレーにおいて不安定核核半径の相互作用断面積による測定を開始 し、11Li, 14Be, 17B などの中性子過剰核に中性子ハロー構造を発見した。それ以来、相互作用断面積また は反応断面積は、中性子まで含めた核半径を調べるための良いプローブとなることがわかってきている。 このこと元に、我々は反応断面積のエネルギー依存性・アイソスピン依存性を利用し、核半径というスカ ラー量だけでなく、陽子・中性子・核子密度分布といった原子核の表面構造を詳細に明らかにする方法を 確立してきた。また、反応断面積という積分量に加えて、核子ピックアップやストリッピングなど、核子 移行反応の断面積も、核構造やときには核子間相互作用に対して重要な情報を与える場合がある。 本講演では、反応断面積測定により調べた軽核領域の陽子・中性子・核子密度分布や、Ca 領域核半径 の最新解析状況、核子移行反応断面積の測定による核構造研究の可能性などについて紹介・議論を行い たい。

q950.pdf
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第949回九大原子核セミナー

2018年6月22日(金) 16:30〜18:00

講師: 初田 哲男 氏 (理化学研究所)
演題:Baryon-Baryon Interactions from Lattice QCD 格子量子色力学 に基づくバリオン間相互作用

場所:ウェスト1号館7階 物理セミナー室2 (W1-A-722室)

概要:
近年、格子 QCD に基づいた第一原理計算によりバリオン間の相互作用が導出できる手法 (HAL QCD 法)が確立し、京コンピュータを用いた物理点近傍での計算が行われている。本 セミナーでは、HAL QCD 法の基礎について概観したのち、我々HAL QCD 共同研究グループ の最新の成果であるダイオメガ(ストレンジクォーク6つからなる新しい結合状態)の予言に ついて発表する。

q949.pdf
九大セミナー | - | -

第948回九大原子核セミナー

2018年5月31日(金) 16:30〜18:00

講師: 伊藤 誠 氏 (関西大学)
演題:Evidence of an enhanced nuclear radius of the α-halo state via α + 12C inelastic scattering

場所:ウェスト1号館7階 物理会議室 (W1-A-723室)

概要:
Evidence of the enhanced nuclear radius in the Hoyle rotational state, 2_2^+ , is derived from the differential cross sections in the α+12C inelastic scattering. The prominent shrinkage is observed in the differential cross section of the 2_2^+ state in comparison to the yrast 2_1^+ state, and this shrinkage is a first evidence of the enhanced nuclear radius, which is originated from the 3α structure in the 2_2^+ state. The diffraction formula, such as Blair’s phase rule, is applied to the differential cross sections, and the present analysis predicts about 0.6 -- 1.0 fm enhancement in the nuclear radius of the 2_2^+ state in comparison to the radius of the ground state. We also show the extension of the our analysis to the production reaction of a Lambda hyper nucleus, such as 13C(K−, π−)13C. The probe of the enhanced nuclear radius in the Λ13C = 3α + Λ structure will be discussed.

q948.pdf
九大セミナー | - | -

第947回九大原子核セミナー

2018年4月20日(金) 16:30〜18:00

講師: Dalibor Skoupil 氏 (九州大学)
演題:Electromagnetic Production of Hyperons

場所:ウェスト1号館7階 物理会議室 (W1-A-723室)

概要:
The aim of this presentation is to provide an overview of the strangeness photo- and electroproduction reaction, especially K+ Lambda photo- and electroproduction off proton, and report on recent progress in this field. The kaon photoproduction on the proton is studied either in the resonance region, using an isobar model, or in the resonance region and beyond, exploiting a hybrid Regge-plus-resonace (RPR) framework. The higher-spin nucleon, spin-3/2 and spin-5/2, and hyperon, spin-3/2, resonances have been included in the model utilizing the consistent formalism by Pascalutsa and they were found to play an important role in data description. A further upgrade of our model was accomplished by implementing energy-dependent widths of nucleon resonances, which leads to a different choice of hadron form factor with much softer values of cutoff parameter for the resonant part. For a reliable description of electroproduction, the necessity of including longitudinal couplings of nucleon resonances to virtual photons was revealed. The free parameters of the models were fitted either solely to photoproduction data or to both photo- and electroproduction data from many collaborations, resulting in BS1 isobar model and RPR fit for photoproduction and a BS3 version of isobar model eligible also for electroproduction description. All models provide a reasonable overall description of the data in the kinematic regions where the free parameters were adjusted. Even though the kaon photoproduction takes place in the third-resonance region with many resonant states, the total number of included resonances, 15, 16, and 10 in the BS1, BS3, and RPR models, respectively, is quite moderate and it is comparable with amounts of resonances in other models. Moreover, the majority of nucleon resonances chosen in this analysis coincide with those selected in the Bayesian analysis with the RPR model as the states contributing to this process with the highest probability.

q947.pdf
九大セミナー | - | -

第944回九大原子核セミナー

2018年3月1日(木) 16:30〜18:00

講師:Jirina Stone 氏(Tennessee大学)

演題:Superheavy nuclei in the Quark-Meson Coupling model

場所:ウェスト1号館7階 物理会議室 (W1-A-723室)

概要:
The fundamental problem of low energy nuclear structure is the understanding the change of the free nucleon-nucleon force in the nuclear medium. Commonly used forces of the Skyrme or Gogny type, with their empirical medium density dependence, cannot be determined uniquely. Hundreds of such forces have been constructed, fitting their numerous correlated parameters to selected experimental data. We report a single, four-parameter form of the density dependent effective nucleon-nucleon force based on modification of the nucleon structure in-medium on the quark level, which represents a new paradigm for nuclear physics. The model yields results for the ground-state binding energies, electromagnetic properties and shapes of even-even nuclei, from the lightest to superheavy, in agreement with experiment within less than a few percent [1].
I will discuss the latest results obtained for binding energies, deformations and single-particle energies of even-even nuclei in the region of 100 < Z < 110 and their comparison with available experimental data. Extension of the model to nuclei with the atomic number up to 120, predicted shell closures and attempts to identify an island of stability in the superheavy region will be reported [2].

[1] J.R.Stone, P.A.M. Guichon, P.-G. Reinhard and A.W. Thomas,
Phys.Rev.Lett. 116, 092501 (2016)
[2] J.R.Stone, P.A.M.Guichon and A.W.Thomas, https://arxiv.org/abs/1706.01153v1

q944.pdf
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