東京大学 原子核科学研究センター

Center for Nuclear Study, The University of Tokyo

    最近の投稿

    CNS Seminar by Prof. Angela Bonaccorso (Mar13)

    Place: Nishina-hall (onsite)

    Date: Mar. 13 (Wed) 13:00(-14:30)

    Speaker: Prof. Angela Bonaccorso (INFN-Pisa)

    Title: Phenomenological and ab-initio optical potentials for nucleon-12C scattering

    Abstract: Absolute values of neutron knockout cross sections from exotic projectile depend strongly on the optical potentials used to describe the core-target interaction and the neutron-target final state interaction. The strong dependence on other ingredients of the calculations, such as initial state wave function and method used to calculate the cross section have been also discussed at length in the past. Recently C. Hebborn , T.R. Whitehead, A.E. Lovell and F.M. Nunes PRC108.014601.2023 quantified the dependence on the optical potentials by a Bayesian analysis. On the other hand in a recent publication we studied the imaginary part of the nucleon-12C and nucleus-12C optical potential (I. Moumene and A.B, PRC108, 044609 (2023)) with the aim of finding the potentials that would best describe the reaction cross sections and eventually the stripping part of knockout. Now we concentrate on the real part of the n-12C potential and its effects on the elastic scattering angular distribution and total elastic cross sections. An important point to discuss is the method used to normalize the experimental distributions. This is necessary to then describe the diffractive part of knockout.

    Posted on 4 Mar, 2024

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    OEDO-SHARAQ研究成果のプレスリリース

    OEDOとSHARAQを用いた放射性同位体79Seの核変換データの研究成果がPhysics Letters Bに出版され、 プレスリリースを行いました(「長寿命核廃棄物の減容および宇宙での元素の起源の解明へ」)。成果記事について英国の文学部の教授より詩が送られました

    Posted on 23 Feb, 2024

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    RIKEN RIBF + CNS Seminar by Prof. Yi-Hua Lam (Feb27)

    Place: Nishina Hall, RIKEN Wako Campus

    Date: Feb. 27 (Tue) 13:30 - 15:00

    Speaker: Prof. Yi-Hua Lam (Institute of Modern Physics, Chinese Academy of Sciences)

    Title: Sensitivity of the SAX J1808.4−3658 Photospheric Radius Expansion Bursts to Thermonuclear Reaction-Rate Variations

    Abstract: More than half of the discovered Type-I X-ray bursters generate photospheric radius expansion (PRE) bursts. Nevertheless, the PRE bursting mechanism is not adequately understood due to the intricate thermo-hydrodynamics, varying accretion rates and non-constant recurrence times throughout a series of consecutive type-I X-ray bursts (XRBs). A set of PRE-burst models matching with observations are highly desired within the community to understand the burst mechanism and evolution of thermo-hydrodynamics, and to unfold the information embedded in X-ray signals, especially the properties of the accreting neutron star of a low-mass X-ray binary, nucleosynthesis, and burst ash composition. To construct these PRE models, identifying and reducing the uncertainties of important thermonuclear reactions are our prime aims. Here we investigate the sensitivity of PRE-burst models for the SAX J1808.4–3658 X-ray source on the uncertainties in (alpha, p), (alpha, gamma), (p, alpha), and (p, gamma) nuclear reaction rates. The fully self-consistent PRE-burst models consider the mutual influence between changes in extreme astrophysical conditions and changes in nuclear energy generation throughout the evolution of the sequential bursts. These PRE-burst models are instantiated from the state-of-the-art one-dimensional multi-zone thermo-hydrodynamic stellar evolution code, KEPLER. The impacts of all relevant reaction rates of proton-rich isotopes up to around mass 80 are individually studied by scaling up and down the respective reaction rate for a factor of 10. We identify and present a number of uncertain reaction rates that significantly influence the reproduction of observables (i.e., burst light curves, fluences, and recurrence times) and the prediction of burst ashes. The PRE-burst model is more sensitive to the change of reaction rates compared to all previous sensitivity studies. Moreover, this is the first XRB sensitivity study based on direct comparison with observations. In this talk, I will present the sensitivity-study results, deepening our understanding of the nuclear processes that shape observables of PRE bursts, and serving as a guidance for future nuclear astrophysics to reduce nuclear uncertainties in PRE models.

    Posted on 16 Feb, 2024

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