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pp→ppπ0 near the Threshold in Pionless Effective Field Theory
Shung-ichi Ando 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.2
In this talk, we review our recent calculation for the pp→ppπ0 reaction near the threshold in pionless effective field theory with a di-baryon and external pions.
A Renormalization Method for a Three-Boson System with a Triboson Field
Shung-Ichi Ando 한국물리학회 2017 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.70 No.4
A renormalization method that introduces an auxiliary field to represent a three-body bound state is studied in a three-boson system with a triboson field. A cutoff dependence in the threeboson system emerges as a limit cycle, and the cyclic singularity is renormalized by employing two methods: a standard method and the auxiliary field method. For each method, different sets of diagrams are involved for renormalization; thus, we numerically study three quantities: a counter term for renormalization, the scattering length of s-wave boson-diboson scattering, and the normalized wavefunction. We confirm that the two methods lead to the same result.
Elastic ff-12C Scattering with the Ground State of 16O at Low Energies in Effective Field Theory
Shung-Ichi Ando 한국물리학회 2018 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.73 No.10
Inclusion of the ground state of 16O is investigated for a study of elastic ff-12C scattering for the l = 0 channel at low energies in effective field theory. We employ a Markov chain Monte Carlo method for the parameter fitting and find that the uncertainties of the fitted parameters are significantly improved compared to those of our previous study. We then calculate the asymptotic normalization constants of the 0+ states of 16O and compare them with the experimental data and the previous theoretical estimates. We discuss implications of the results of the present work.
American Physical Society 2018 Physical Review C Vol.97 No.1
<P>The elastic alpha-C-12 scattering for l = 0,1,2,3 channels at low energies is studied, including the energies of excited bound states of O-16, in effective field theory. A new renormalization method is introduced due to the large suppression factor produced by the Coulomb interaction when the effective range parameters are fitted to the phase sift data. After fitting the parameters, the asymptotic normalization constants of the 0(2)(+), 1(1)(-), 2(1)(+), 3(1)(-) states of O-16 are calculated. The uncertainties when the amplitudes are interpolated to the stellar energy region of the C-12(alpha,gamma)O-16 reaction are also discussed.</P>
Effective Range Expansion and Elastic α-12C Scattering at Low Energies
윤효은,Shung-Ichi Ando 한국물리학회 2019 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.75 No.3
The elastic α-12C scattering for l = 0, 1, 2, 3 at low energies is studied by using the scattering amplitudes represented in terms of the effective range expansion where four effective range terms are included for l = 0,1,2, and five for l = 3. The first effective range terms are fixed by using the binding energies of the 0+2 , 1−1 , 2+1 , and 3−1 ( lπi−th ) states of 16O, and the other parameters are fitted to the phase shift data. After fitting the parameters to the data, we find that the broad resonant 1−2 and 3−2 states of 16O are well incorporated, without the need to introduce any other parameterization, such as the Breit-Wigner formula or the Pade approximation, in the amplitudes while the narrow resonant 0+3 and 2+2 states are not. We also calculate the asymptotic normalization coefficients for the bound states of 16O and compare them with the previous results in other works.
Sangyeong Son,Shung-Ichi Ando,Yongseok Oh 한국물리학회 2022 새물리 Vol.72 No.4
The radiative proton capture on <SUP>15</SUP>N targets, i.e., <SUP>15</SUP>N(p, γ)<SUP>16</SUP>O, is an important thermonuclear reaction of the CNO cycle in stellar environments. This reaction is a key process in the cycle because it initiates the NO cycle by producing <SUP>16</SUP>O. In this study, we investigated the <SUP>15</SUP>N(p, γ)<SUP>16</SUP>O reaction within the framework of cluster effective field theory. We construct an effective Lagrangian to describe the reaction at stellar energies and calculate the astrophysical S factor. The parameters of our calculations, such as low-energy constants, resonance energy, and decay width of the <SUP>16</SUP>O resonance are determined by fitting empirical data of the S factor at the range of 72.8 keV ≤ E<SUB>cm</SUB> ≤ 368.3 keV. The S factor value for this reaction at extremely low energy is then determined to be S(E = 0) = 30.4 keV·b, which is consistent with the estimates of R-matrix approaches.<br/>
Song, Young-Ho,Ando, Shung-Ichi,Hyun, Chang Ho American Physical Society 2017 Physical Review C Vol.96 No.1
<P>Spin-polarization observables of deuteron photodisintegration at lowenergies are studied in a pionless effectivefield theory up to next-to-next-to-leading order (NNLO). The total and differential cross sections, induced neutron polarization P-y', and tensor analyzing powers T-20 and T-22 of the process are calculated at photon energies from the breakup threshold to 20 MeV. We find that the NNLO corrections in the cross sections and P-y' converge well whereas they turn out to be important contributions in T-20 and T-22. We discuss the discrepancy between theory and experiment in P-y' still persisting as well as an implication of our result to the first measurement of T-20 at low energies in the High Intensity Gamma-Ray Source facility at Duke University.</P>