九大原子核セミナー

2020年7月10日(金) 16:00〜17:30

講師：Pascal Naidon 氏 (理研仁科加速器科学研究センター)
演題：QCD-like phase diagram of resonantly interacting SU(3) Fermi gases
場所：※オンラインセミナー

概要(Abstract)： Systems of fermions with two components (such as spin-1/2 electrons) are well-known to lead the phenomenon of Cooper pairing of different components, leading to fermionic superfluidity. Pair formation and superfluidity also occurs in fermionic systems with 3 components, leading to the so-called "colour superfluidity" where each of three different components (regarded as colours) can pair with one of the two others. However, another phenomenon can occur in these systems: the formation of trimers of three different components, due to the Efimov effect.

The interplay between Cooper pairing and the Efimov effect makes the phase diagram of such systems non trivial. Using an in-medium three-body equation and a non-self-consistent T-matrix approximation, we obtain a first insight into the temperature-density phase diagram of an SU(3)-symmetric unitary Fermi, that is to say a three-component fermionic system where all the scattering lengths between different components are infinite. The obtained phase diagram consists of three phases (trimer, normal, and colour superfluid phases) and bears some similarities with the conjectured phase diagram of quantum chromodynamics (QCD) at finite density and temperature.

2020年6月26日(金) 15:00〜

講師：Ying Zhang 氏 (天津大学)
演題：A simple quantum many-body system – neutron drop
場所：※オンラインセミナー

概要(Abstract)：A neutron drop is a system composed only of neutrons trapped by artificial external fields [1]. This simple system can be easily calculated by both the ab initio approach and energy-density functional theory. Therefore, the ab initio solutions for a neutron drop can be used as pseudo-data to calibrate and improve the effective Hamiltonians and density functionals in nuclear physics [2,3]. In this seminar, I will introduce our investigation on neutron drop by using the energy- density functional theories, including the following aspects: the origin of the spin- orbit and pseudospin-orbit splittings ’evolution in neutron drop; the pairing [4] and the deformation effects on the neutron drop.

[1] B. S. Pudliner, A. Smerzi, J. Carlson, V. R. Pandharipande, S. C. Pieper, D. G. Ravenhall, Neutron drops and skyrme energy-density functionals, Phys. Rev. Lett. 76 (1996) 2416-2419.
[2] S. Gandolfi, J. Carlson, S. C. Pieper, Cold neutrons trapped in external elds, Phys. Rev. Lett. 106 (2011) 012501.
[3] S. K. Bogner, R. J. Furnstahl, H. Hergert, M. Kortelainen, P. Maris, M. Stoitsov, J. P. Vary, Testing the density matrix expansion against ab initio calcu-
lations of trapped neutron drops, Phys. Rev. C 84 (2011) 044306.
[4] Y. H. Ge, Y. Zhang, J. N. Hu, Effects of pairing correlation on neutron drop, Sci. China Physics, Mech. Astron. 63 (2020) 242011.

2020年6月5日(金) 16:00〜

講師：Qian Wu 氏 (Nanjing Univ.)
演題：Structure of Be9-Lambda with alpha-alpha-Lambda microscopic cluster model
場所：※オンラインセミナー

概要(Abstract)：We study the structure of Be9-Lambda in the framework of three body alpha+alpha+Lambda cluster model by using the realistic NN and YN interaction.
With applying the complex scaling method into Gaussian expansion method,
we obtain both the energy and decay width of the resonances of Be9-Lambda(T=0).
The three particular structures of Be9-Lambda: Be8 analogue states,
Be9-Lambda genuine states and Be9 analogue states are confirmed with calculating the
overlap probability with the SU(3) shell model configurations.
We find several resonances which are pointed out by the previous studies of Be9-Lambda, are missing.
The new states of Be9-Lambda are also found at a high energy region and there might appear new structures.

2020年3月9日(月) 16:30〜18:00 17:00~18:30 (時間が変更になりました)

講師：渡邉 慎氏 (岐阜工業高等専門学校)
演題：Extracting each component from discretized breakup cross sections in multi-breakup-channel reactions
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(Abstract)：
The continuum-discretized coupled-channel method (CDCC) proposed in
Kyushu University is still one of the most powerful methods of
describing breakup reactions. As a dramatic development in the last
fifteen years, CDCC can treat multi-breakup-channel reactions beyond
simple three-body scattering, i.e., four-body CDCC and three-body
scattering with core excitation. For example, in 6Li scattering
(n+p+α+T, T is a target), the four-body-breakup channel (n+p+α+T)
and the three-body-breakup channel (d+α+T) coexist, and they are
coupled to each other during the scattering. In CDCC, those two
channels are precisely taken into account on an equal footing but the
corresponding breakup cross sections (BUXs) are obtained as an
admixture of these channels because of its discretization. It is
desired to separately calculate those BUXs. In this talk, we propose
an approximate method of extracting each component from the
discretized breakup cross sections. We show the validity of the
approximation method and discuss reaction dynamics beyond simple
three-body scattering.

2020年3月16日(月) 16:30〜18:00 (日時が変更になりました)

講師：山中 長閑 氏 (Department of Physics, University of Massachusetts Amherst)
演題：Nuclear electric dipole moment and new physics beyond the standard model
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(Abstract)：
The electric dipole moment (EDM) of light nuclei is a very sensitive probe of CP violation beyond the standard model which may be measured in future experiments. Nuclei are particularly interesting since the nuclear level CP violation is not suppressed by the atomic screening effect pointed by Schiff. However, their sensitivity on hadronic CP violation strongly depends on the nuclear structure due to the many-body effect. In this talk, we present the results of our theoretical evaluations of the EDM of light nuclei using few-body methods, and show the prospect for the discovery of new physics beyond the standard model.