arXiv subjects

T. Udagawa

Publications and source records attributed to T. Udagawa.

10 recordsLinked to original sources

arXiv2010

Extended Optical Model Analyses of Elastic Scattering and Fusion Cross Section Data for the 9Be+28Si, 144Sm, and 208Pb Systems at Near-Coulomb-Barrier Energies using Double Folding Potential

Based on the extended optical model with the double folding potential, in which the polarization potential is decomposed into direct reaction (DR) and fusion parts, simultaneous $χ^{2}$ analyses are performed of elastic scattering and fusion cross section data for the $^{9}$Be+$^{28}$Si, $^{144}$Sm, and $^{208}$Pb systems at near-Coulomb-barrier energies. We find that the real part of the resultant DR part of the polarization potential is systematically repulsive for all the targets considered, which is consistent with the results deduced from the Continuum Discretized Coupled Channel (CDCC) calculations taking into account the polarization effects due to breakup. Further, it is found that both DR and fusion parts of the extracted polarization potentials satisfy the dispersion relation.

nucl-th↗

arXiv2008

Extended Optical Model Analyses of Elastic Scattering and Fusion Cross Section Data for the $^{12}$C+$^{208}$Pb System at Near-Coulomb-Barrier Energies by using a Folding Potential

Simultaneous $χ^{2}$ analyses are performed for elastic scattering and fusion cross section data for the $^{12}$C+$^{208}$Pb system at near-Coulomb-barrier energies by using the extended optical model approach in which the polarization potential is decomposed into direct reaction (DR) and fusion parts. Use is made of the double folding potential as a bare potential. It is found that the experimental elastic scattering and fusion data are well reproduced without introducing any normalization factor for the double folding potential and also that both DR and fusion parts of the polarization potential determined from the $χ^{2}$ analyses satisfy separately the dispersion relation. Furthermore, it is shown that the imaginary parts of both DR and fusion potentials at the strong absorption radius change very rapidly, which results in a typical threshold anomaly in the total imaginary potential as observed with tightly bound projectiles such as $α$-particle and $^{16}$O.

nucl-th↗

arXiv2007

Extended Optical Model Analyses of Elastic Scattering and Fusion Cross Section Data for the 7Li+208Pb System at Near-Coulomb-Barrier Energies using the Folding Potential

Simultaneous $χ^{2}$ analyses previously made for elastic scattering and fusion cross section data for the $^{6}$Li+$^{208}$Pb system is extended to the $^{7}$Li+$^{208}$Pb system at near-Coulomb-barrier energies based on the extended optical model approach, in which the polarization potential is decomposed into direct reaction (DR) and fusion parts. Use is made of the double folding potential as a bare potential. It is found that the experimental elastic scattering and fusion data are well reproduced without introducing any normalization factor for the double folding potential and that both the DR and fusion parts of the polarization potential determined from the $χ^{2}$ analyses satisfy separately the dispersion relation. Further, we find that the real part of the fusion portion of the polarization potential is attractive while that of the DR part is repulsive except at energies far below the Coulomb barrier energy. A comparison is made of the present results with those obtained from the Continuum Discretized Coupled Channel (CDCC) calculations and a previous study based on the conventional optical model with a double folding potential. We also compare the present results for the $^7$Li+$^{208}$Pb system with the analysis previously made for the $^{6}$Li+$^{208}$Pb system.

nucl-th↗

arXiv2006

Extended Optical Model Analyses of Elastic Scattering and Fusion Cross Sections for 6Li + 208Pb System at Near-Coulomb-Barrier Energies by using Folding Potential

Based on the extended optical model approach in which the polarization potential is decomposed into direct reaction (DR) and fusion parts, simultaneous $χ^{2}$ analyses are performed for elastic scattering and fusion cross section data for the $^{6}$Li+$^{208}$Pb system at near-Coulomb-barrier energies. A folding potential is used as the bare potential. It is found that the real part of the resultant DR part of the polarization potential is repulsive, which is consistent with the results from the Continuum Discretized Coupled Channel (CDCC) calculations and the normalization factors needed for the folding potentials. Further, it is found that both DR and fusion parts of the polarization potential satisfy separately the dispersion relation.

nucl-th↗

arXiv2005

Extended Optical Model Analyses of Elastic Scattering, Direct Reaction, and Fusion Cross Sections for the 9Be + 208Pb System at Near-Coulomb-Barrier Energies

Based on the extended optical model approach in which the polarization potential is decomposed into direct reaction (DR) and fusion parts, simultaneous $χ^{2}$ analyses are performed for elastic scattering, DR, and fusion cross section data for the $^{9}$Be+$^{208}$Pb system at near-Coulomb-barrier energies. Similar $χ^{2}$ analyses are also performed by only taking into account the elastic scattering and fusion data as was previously done by the present authors, and the results are compared with those of the full analysis including the DR cross section data as well. We find that the analyses using only elastic scattering and fusion data can produce very consistent and reliable predictions of cross sections particularly when the DR cross section data are not complete. Discussions are also given on the results obtained from similar analyses made earlier for the $^{9}$Be+$^{209}$Bi system.

nucl-th↗

arXiv2002

A Novel Method for the Solution of the Schroedinger Eq. in the Presence of Exchange Terms

In the Hartree-Fock approximation the Pauli exclusion principle leads to a Schroedinger Eq. of an integro-differential form. We describe a new spectral noniterative method (S-IEM), previously developed for solving the Lippman-Schwinger integral equation with local potentials, which has now been extended so as to include the exchange nonlocality. We apply it to the restricted case of electron-Hydrogen scattering in which the bound electron remains in the ground state and the incident electron has zero angular momentum, and we compare the acuracy and economy of the new method to three other methods. One is a non-iterative solution (NIEM) of the integral equation as described by Sams and Kouri in 1969. Another is an iterative method introduced by Kim and Udagawa in 1990 for nuclear physics applications, which makes an expansion of the solution into an especially favorable basis obtained by a method of moments. The third one is based on the Singular Value Decomposition of the exchange term followed by iterations over the remainder. The S-IEM method turns out to be more accurate by many orders of magnitude than any of the other three methods described above for the same number of mesh points.

physics.atom-ph↗

arXiv2001

Simultaneous Optical Model Analyses of Elastic Scattering, Breakup, and Fusion Cross Section Data for the $^{6}$He + $^{209}$Bi System at Near-Coulomb-Barrier Energies

Based on an approach recently proposed by us, simultaneous $χ^{2}$-analyses are performed for elastic scattering, direct reaction (DR) and fusion cross sections data for the $^{6}$He+$^{209}$Bi system at near-Coulomb-barrier energies to determine the parameters of the polarization potential consisting of DR and fusion parts. We show that the data are well reproduced by the resultant potential, which also satisfies the proper dispersion relation. A discussion is given of the nature of the threshold anomaly seen in the potential.

nucl-th↗

arXiv2001

Semi-classical Characters and Optical Model Description of Heavy Ion Scattering, Direct Reactions, and Fusion at Near-barrier Energies

An approach is proposed to calculate the direct reaction (DR) and fusion probabilities for heavy ion collisions at near-Coulomb-barrier energies as functions of the distance of closest approach D within the framework of the optical model that introduces two types of imaginary potentials, DR and fusion. The probabilities are calculated by using partial DR and fusion cross sections, together with the classical relations associated with the Coulomb trajectory. Such an approach makes it possible to analyze the data for angular distributions of the inclusive DR cross section, facilitating the determination of the radius parameters of the imaginary DR potential in a less ambiguous manner. Simultaneous $χ^{2}$-analyses are performed of relevant data for the $^{16}$O+$^{208}$Pb system near the Coulomb-barrier energy.

nucl-th↗

arXiv2000

Can Doubly Strange Dibaryon Resonances be Discovered at RHIC?

The baryon-baryon continuum invariant mass spectrum generated from relativistic nucleus + nucleus collision data may reveal the existence of doubly-strange dibaryons not stable against strong decay if they lie within a few MeV of threshold. Furthermore, since the dominant component of these states is a superposition of two color-octet clusters which can be produced intermediately in a color-deconfined quark-gluon plasma (QGP), an enhanced production of dibaryon resonances could be a signal of QGP formation. A total of eight, doubly-strange dibaryon states are considered for experimental search using the STAR detector (Solenoidal Tracker at RHIC) at the new Relativistic Heavy Ion Collider (RHIC). These states may decay to Lambda-Lambda and/or proton-Cascade-minus, depending on the resonance energy. STAR's large acceptance, precision tracking and vertex reconstruction capabilities, and large data volume capacity, make it an ideal instrument to use for such a search. Detector performance and analysis sensitivity are studied as a function of resonance production rate and width for one particular dibaryon which can directly strong decay to proton-Cascade-minus but not Lambda-Lambda. Results indicate that such resonances may be discovered using STAR if the resonance production rates are comparable to coalescence model predictions for dibaryon bound states.

nucl-ex↗

arXiv1996

Damping mechanisms of the Delta resonance in nuclei

The damping mechanisms of the Delta(1232) resonance in nuclei are studied by analyzing the quasi-free decay reactions 12C(pi+,pi+ p)11B and 12C(3He,t pi+ p)11B and the 2p emission reactions 12C(pi+,pp)10B and 12C(3He,t pp)10B. The coincidence cross sections are calculated within the framework of the isobar-hole model. It is found that the 2p emission process induced by the decay of the Delta resonance in the nucleus can be consistently described by a pi+rho+g' model for the Delta+N -> N+N decay interaction.

nucl-th↗