A. Sait Umar

A. Sait Umar

Vanderbilt University

H-index: 49

North America-United States

About A. Sait Umar

A. Sait Umar, With an exceptional h-index of 49 and a recent h-index of 28 (since 2020), a distinguished researcher at Vanderbilt University, specializes in the field of Nuclear Theory, Computational Physics.

His recent articles reflect a diverse array of research interests and contributions to the field:

A theoretical study on quasifission and fusion–fission processes in heavy-ion collisions

Multinucleon transfer mechanism in Gd 160+ W 186 collisions in stochastic mean-field theory

Shell effects in fission and quasi-fission reactions

Description of multinucleon transfer mechanism for and reactions in quantal transport approach

Description of the multinucleon transfer mechanism for and reactions in a quantal transport approach

Study of multinucleon transfer mechanism in collisions in stochastic mean-field theory

Role of isospin composition in low energy nuclear fusion

Cluster model of in the density functional theory framework

A. Sait Umar Information

University

Vanderbilt University

Position

Professor of Physics

Citations(all)

6700

Citations(since 2020)

2379

Cited By

5415

hIndex(all)

49

hIndex(since 2020)

28

i10Index(all)

108

i10Index(since 2020)

72

Email

University Profile Page

Vanderbilt University

A. Sait Umar Skills & Research Interests

Nuclear Theory

Computational Physics

Top articles of A. Sait Umar

A theoretical study on quasifission and fusion–fission processes in heavy-ion collisions

Authors

ARDA Kayaalp,SE Ocal,B Yaprakli,MERT Arik,S Ayik,OSMAN Yilmaz,AS Umar

Journal

The European Physical Journal A

Published Date

2024/4/1

The stochastic mean-field (SMF) technique beyond the time-dependent-Hartree-Fock approach is used to explore the primary mass yields of quasifission fragments in the reaction at the bombarding energy = 238.5 MeV, reaction at = 237 MeV, and in the reaction at = 151.1 MeV. A statistical de-excitation model, GEMINI++ code, is used for calculating the primary mass yields of fusion–fission fragments after the de-excitation processes of primary products in the same systems. The obtained results are compared with available experimental data. Analysis of SMF and GEMINI++ calculations exhibit a good agreement with the corresponding experimental results, signifying the reliability of our approach in describing the fragment mass yields for the specific reaction systems.

Multinucleon transfer mechanism in Gd 160+ W 186 collisions in stochastic mean-field theory

Authors

Osman Yılmaz,Mert Arık,E Erbayri,AS Umar

Published Date

2023/11/1

The multinucleon transfer mechanism in Gd160+W186 collisions is investigated in the framework of quantal transport description, based on the stochastic mean-field (SMF) theory. The SMF theory provides a microscopic approach for nuclear dynamics beyond the time-dependent Hartree-Fock approach by including mean-field fluctuations. Cross sections for the primary fragment production are determined in the quantal transport description and compared with the available data.

Shell effects in fission and quasi-fission reactions

Authors

Cedric Simenel,K Godbey,H Lee,P McGlynn,AS Umar

Journal

Journal of Physics: Conference Series

Published Date

2023/9/1

Quantum shell effects are responsible for asymmetric fission. They are also expected to affect the formation of fission fragments in quasi-fission reactions occurring in heavy-ion collisions. Systematic time-dependent Hartree-Fock simulations of 40–56 Ca+ 176 Yb collisions show that quasi-fission fragment properties share strong similarities with fragments formed in fission of the compound nuclei. This is an indication that similar shell effects are responsible for the final asymmtery in both mechanisms.

Description of multinucleon transfer mechanism for and reactions in quantal transport approach

Authors

M Arik,S Ayik,O Yilmaz,AS Umar

Journal

arXiv preprint arXiv:2308.16027

Published Date

2023/8/30

This work aims to show that the quantal diffusion approach based on the stochastic mean field (SMF) theory is capable of explaining the reaction dynamics observed in MNT reactions. Primary product mass distributions in Ca+Pu reaction at E 203.2 MeV and Kr+Pt reaction at E 324.2 MeV are calculated and compared with the available experimental data.

Description of the multinucleon transfer mechanism for and reactions in a quantal transport approach

Authors

MERT Arik,S Ayik,OSMAN Yilmaz,AS Umar

Journal

Physical Review C

Published Date

2023/12/12

Background: Multinucleon transfer (MNT) reactions involving heavy projectile and target combinations stand as a promising method for synthesizing new neutron-rich exotic nuclei, which may not be possible using hot or cold fusion reactions or fragmentation. Exploring the mechanisms behind MNT reactions is essential and it requires a comprehensive theoretical framework that can explain the physical observables in these reactions.Purpose: This work aims to show that the quantal diffusion approach based on the stochastic mean-field (SMF) theory is capable of explaining the reaction dynamics observed in MNT reactions. Primary product mass distributions in Ca 48+ Pu 244 reaction at E cm= 203.2 MeV and Kr 86+ Pt 198 reaction at E cm= 324.2 MeV are calculated and compared with the available experimental data.Methods: In this work, we utilize the time-dependent Hartree-Fock (TDHF) calculations to …

Study of multinucleon transfer mechanism in collisions in stochastic mean-field theory

Authors

S Ayik,M Arik,E Erbayri,O Yilmaz,AS Umar

Journal

arXiv preprint arXiv:2308.00131

Published Date

2023/7/31

Multinucleon transfer mechanism in collision of system is investigated in the framework of quantal transport description, based on the stochastic mean-field (SMF) theory. The SMF theory provides a microscopic approach for nuclear dynamics beyond the time-dependent Hartree-Fock (TDHF) approach by including mean-field fluctuations. Cross-sections for the primary fragment production are determined in the quantal transport description and compared with the available data.

Role of isospin composition in low energy nuclear fusion

Authors

Christian Ross,Richard Gumbel,Sait Umar

Journal

Bulletin of the American Physical Society

Published Date

2023/11/30

We employ a microscopic approach that examines the impact of isospin dynamics on the process of low energy nuclear fusion along an isotope chain and dependence on deformation. Our method utilizes the density constrained time-dependent Hartree-Fock theory (DC-TDHF), where isoscalar and isovector characteristics of the energy density functional (EDF) are examined in turn. This approach is applied to a series of fusion interactions of 176Yb with increasingly neutron rich isotopes of Calcium. By evaluating the contributions from the isoscalar and isovector components of the EDF, we look to quantify the influence of isospin composition on the conditions under which fusion is most likely to take place. Our findings reveal that, in non-symmetric systems, the isovector dynamics play a significant role. It's typical effect is a reduction in the potential barrier, which turns into enhancement for neutron-rich systems.

Cluster model of in the density functional theory framework

Authors

AS Umar,K Godbey,Cedric Simenel

Journal

Physical Review C

Published Date

2023/6/14

We employ the constrained density functional theory to investigate cluster phenomena for the C 12 nucleus. The proton and neutron densities are generated from the placement of three He 4 nuclei (α particles) geometrically. These densities are then used in a density constrained Hartree-Fock calculation that produces an antisymmetrized state with the same densities through energy minimization. In the calculations no a priori analytic form for the single-particle states is assumed and the full energy density functional is utilized. The geometrical scan of the energy landscape provides the ground state of C 12 as an equilateral triangular configuration of three α s with molecular bond like structures. The use of the nucleon localization function provides further insight to these configurations. One can conclude that these configurations are a hybrid between a pure mean-field and a pure α particle condensate. This …

Multinucleon transfer mechanism in collisions in stochastic mean-field theory

Authors

Sakir Ayik,Mert Arik,Eda Erbayri,Osman Yilmaz,Ahmet S Umar

Journal

Physical Review C

Published Date

2023/11/20

The multinucleon transfer mechanism in Gd 160+ W 186 collisions is investigated in the framework of quantal transport description, based on the stochastic mean-field (SMF) theory. The SMF theory provides a microscopic approach for nuclear dynamics beyond the time-dependent Hartree-Fock approach by including mean-field fluctuations. Cross sections for the primary fragment production are determined in the quantal transport description and compared with the available data.

Multinucleon transfer mechanism in collisions using the quantal transport description based on the stochastic mean-field approach

Authors

S Ayik,MERT Arik,OSMAN Yilmaz,BÜLENT Yilmaz,AS Umar

Journal

Physical Review C

Published Date

2023/1/10

Production cross sections of heavy neutron-rich isotopes are calculated by employing quantal transport description in Cf 250+ Th 232 collisions. This quantal transport description is based on the stochastic mean-field approach, and it provides a microscopic approach beyond time-dependent Hartree-Fock theory to include mean-field fluctuations. Deexcitation of primary fragments is determined by employing the statistical GEMINI++ code. Calculations provide predictions for production cross sections of neutron rich transfermium isotopes without any adjustable parameters.

Microscopic study of the fusion reactions and the effect of the tensor force

Authors

Xiang-Xiang Sun,Lu Guo,AS Umar

Journal

Physical Review C

Published Date

2022/3/1

We provide a microscopic description of the fusion reactions between Ca 40, 48 and Ni 78. The internuclear potentials are obtained using the density-constrained (DC) time-dependent Hartree-Fock (TDHF) approach and fusion cross sections are calculated via the incoming wave boundary condition method. By performing DC-TDHF calculations at several selected incident energies, the internuclear potentials for both systems are obtained and the energy-dependence of fusion barrier are revealed. The influence of tensor force on internuclear potentials of Ca 48+ Ni 78 is more obvious than those of Ca 40+ Ni 78. By comparing the calculated fusion cross sections between Ca 40+ Ni 78 and Ca 48+ Ni 78, an interesting enhancement of subbarrier fusion cross sections for the former system is found, which can be explained by the narrow width of internuclear potential for Ca 40+ Ni 78 while the barrier heights and …

Theoretical uncertainty quantification for heavy-ion fusion

Authors

Kyle Godbey,AS Umar,Cedric Simenel

Journal

Physical Review C

Published Date

2022/11/18

Despite recent advances and focus on rigorous uncertainty quantification for microscopic models of quantum many-body systems, the uncertainty on the dynamics of those systems has been underexplored. To address this, we have used time-dependent Hartree-Fock to examine the model uncertainty for a collection of low-energy, heavy-ion fusion reactions. Fusion reactions at near-barrier energies represent a rich test-bed for the dynamics of quantum many-body systems owing to the complex interplay of collective excitation, transfer, and static effects that determine the fusion probability of a given system. The model uncertainty is sizable for many of the systems studied and the primary contribution arises from static properties that are ill-constrained, such as the neutron radius of neutron-rich nuclei. These large uncertainties motivate the use of information from reactions to better constrain existing models and to …

Microscopic study of the fusion reactions Ca40, 48+ Ni78 and the effect of the tensor force

Authors

Xiang-Xiang Sun,Lu Guo,AS Umar

Journal

Phys. Rev. C

Published Date

2022

We provide a microscopic description of the fusion reactions between and . The internuclear potentials are obtained using the density-constrained (DC) time-dependent Hartree-Fock (TDHF) approach and fusion cross sections are calculated via the incoming wave boundary condition method. By performing DC-TDHF calculations at several selected incident energies, the internuclear potentials for both systems are obtained and the energy-dependence of fusion barrier are revealed. The influence of tensor force on internuclear potentials of is more obvious than those of . By comparing the calculated fusion cross sections between and , an interesting enhancement of subbarrier fusion cross sections for the former system is found, which can be explained by the narrow width of internuclear potential for while the barrier heights and positions are very close to each other. The tensor force suppresses the subbarrier fusion cross sections of both two systems.

Multinucleon transfer mechanism in

Authors

S Ayik,M Arik,O Yilmaz,B Yilmaz,AS Umar

Journal

arXiv preprint arXiv:2210.09106

Published Date

2022/10/17

Production cross-sections of heavy neutron-rich isotopes are calculated by employing quantal transport description in collisions. This quantal transport description is based on the stochastic mean-field (SMF) approach, and it provides a microscopic approach beyond time-dependent Hartree-Fock (TDHF) theory to include mean-field fluctuations. De-excitation of primary fragments is determined by employing the statistical GEMINI++ code. Calculations provide predictions for production cross-sections of neutron rich transfermium isotopes without any adjustable parameters.

Impact of tensor force on quantum shell effects in quasifission reactions

Authors

Liang Li,Lu Guo,K Godbey,AS Umar

Journal

Physics Letters B

Published Date

2022/10/10

Quantum shell effects drive many aspects of many-body quantal systems and their interactions. Among these are the quasifission reactions that impede the formation of a compound nucleus in superheavy element (SHE) searches. Fragment production in quasifission is influenced by shell effects as a nontrivial manifestation of microscopic dynamics hindering the full equilibration of the composite system to form the compound nucleus. In this Letter, we use the microscopic time-dependent Hartree-Fock (TDHF) theory to study 48 Ca+ 249 Bk collisions to investigate the influence of the tensor component of the effective nucleon-nucleon interaction. The results show that the inclusion of the tensor force causes the spherical shell effect to become more prominent, particularly for the neutron number yield whose peak is exactly at magic number N= 126. This suggests that the tensor force plays a compelling role in the …

Multinucleon transfer reactions: a mini-review of recent advances

Authors

Tea Mijatović

Published Date

2022/8/19

Multinucleon transfer reactions, characterized by the exchange of many nucleons at energies in the vicinity of the Coulomb barrier, have been extensively used in the last decades to understand the production of neutron-rich nuclei, as well as to study their structure. In this Mini Review, recent results related to the production mechanism of heavy neutron-rich nuclei obtained with stable and radioactive beams will be discussed together with the results concerning the proton transfer channels. Additionally, newest results from a series of experiments carried out to study nucleon-nucleon correlations for closed-shell and superfluid systems employing the large solid angle magnetic spectrometer PRISMA will be summarized.

Microscopic study on fusion reactions and the effect of tensor force

Authors

Xiang-Xiang Sun,Lu Guo,AS Umar

Journal

arXiv preprint arXiv:2207.13536

Published Date

2022/7/27

We provide a microscopic description of the fusion reactions between Ca and Ni. The internuclear potentials are obtained using the density-constrained (DC) time-dependent Hartree-Fock (TDHF) approach and fusion cross sections are calculated via the incoming wave boundary condition method. By performing DC-TDHF calculations at several selected incident energies, the internuclear potentials for both systems are obtained and the energy-dependence of fusion barrier are revealed. The influence of tensor force on internuclear potentials of is more obvious than those of . By comparing the calculated fusion cross sections between and , an interesting enhancement of sub-barrier fusion cross sections for the former system is found, which can be explained by the narrow width of internuclear potential for while the barrier heights and positions are very close to each other. The tensor force suppresses the sub-barrier fusion cross sections of both two systems.

Quantified impact of the Pauli exclusion principle on the nucleus-nucleus interaction

Authors

Kyle Godbey,Sait Umar,C Simenel

Journal

APS Division of Nuclear Physics Meeting Abstracts

Published Date

2021

The Pauli exclusion principle plays a crucial role as a pillar of many-body quantal systems comprised of fermions. It also induces a``Pauli repulsion''in the interaction between heavy ions. It has been shown in that the Pauli repulsion widens the nucleus-nucleus potential barrier, thus hindering sub-barrier fusion. To extend this picture, we use the Pauli kinetic energy (PKE) obtained by studying the nuclear localization function. This approach is employed in both the static density constrained frozen Hartree-Fock and in the dynamic density constrained time-dependent Hartree-Fock microscopic methods. Significant effects are seen at first contact of the reaction nuclei and deep inside the fusion barrier. Furthermore, varying effects are seen for dynamic proton/neutron contributions inside the barrier, seen as an effect of multinucleon transfer. The PKE is shown to make a significant contribution to statically and dynamically …

Shell effects in quasifission and implications for fission

Authors

Sait Umar,Kyle Godbey,C Simenel

Journal

APS Division of Nuclear Physics Meeting Abstracts

Published Date

2021

Quasifission reactions have been of great interest in recent years particularly in connections with the formation of superheavy elements and a source for producing neutron rich nuclei. Such reactions proceed through regions of periodic table where the dynamical evolution of quantal shell effects influence the formation of final fragments. The time-dependent density functional theory (TDDFT) has been found to be an excellent theoretical tool to study these reactions microscopically [1-4]. In this talk we discuss the recent results for quasifission reactions obtained using the TDDFT. In, particular we focus on the observed shell effects in these calculations and their relevance and/or relationship for shell effects in fission dynamics.

Pauli energy contribution to nucleus-nucleus interaction potentials

Authors

Sait Umar,Kyle Godbey,Cedric Simenel

Journal

APS April Meeting Abstracts

Published Date

2021

In this work we use the nucleon localization function (NLF) approach to demonstrate the contribution of Pauli energy to nucleus-nucleus interaction potentials. This is a follow up on our previous work on assessing the Pauli effect on the formation of potential pockets in ion-ion interaction potentials. Calculations are done using the density-constrained frozen density approach (DCFHF), the dynamical time-dependent density-constrained Hartree-Fock (DC-TDHF) method, as well as the full time-dependent Hartree-Fock (TDHF) method. We also utilize the Pauli localization function (PLF) to better visualize these effects.

See List of Professors in A. Sait Umar University(Vanderbilt University)

A. Sait Umar FAQs

What is A. Sait Umar's h-index at Vanderbilt University?

The h-index of A. Sait Umar has been 28 since 2020 and 49 in total.

What are A. Sait Umar's top articles?

The articles with the titles of

A theoretical study on quasifission and fusion–fission processes in heavy-ion collisions

Multinucleon transfer mechanism in Gd 160+ W 186 collisions in stochastic mean-field theory

Shell effects in fission and quasi-fission reactions

Description of multinucleon transfer mechanism for and reactions in quantal transport approach

Description of the multinucleon transfer mechanism for and reactions in a quantal transport approach

Study of multinucleon transfer mechanism in collisions in stochastic mean-field theory

Role of isospin composition in low energy nuclear fusion

Cluster model of in the density functional theory framework

...

are the top articles of A. Sait Umar at Vanderbilt University.

What are A. Sait Umar's research interests?

The research interests of A. Sait Umar are: Nuclear Theory, Computational Physics

What is A. Sait Umar's total number of citations?

A. Sait Umar has 6,700 citations in total.

What are the co-authors of A. Sait Umar?

The co-authors of A. Sait Umar are Witold Nazarewicz, Cedric Simenel, Paul Stevenson, Alan Calder.

    Co-Authors

    H-index: 110
    Witold Nazarewicz

    Witold Nazarewicz

    Michigan State University

    H-index: 45
    Cedric Simenel

    Cedric Simenel

    Australian National University

    H-index: 33
    Paul Stevenson

    Paul Stevenson

    University of Surrey

    H-index: 31
    Alan Calder

    Alan Calder

    Stony Brook University

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