1 / 17

Tomohiro Oishi Dept. of Phys., Faculty of Science, Univ. of Zagreb, Croatia.

Magnetic dipole excitation and its sum rule for valence nucleon pair. Tomohiro Oishi Dept. of Phys., Faculty of Science, Univ. of Zagreb, Croatia. International Nuclear Physics Conference (INPC) 2019 @ Glasgow, Scotland UK, July 29 th –August 2 nd , 2019. Introduction ( i ). Background

dorris
Download Presentation

Tomohiro Oishi Dept. of Phys., Faculty of Science, Univ. of Zagreb, Croatia.

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Magnetic dipole excitation and its sum rule for valence nucleon pair Tomohiro Oishi Dept. of Phys., Faculty of Science, Univ. of Zagreb, Croatia. International Nuclear Physics Conference (INPC) 2019 @ Glasgow, Scotland UK, July 29th –August 2nd, 2019.

  2. Introduction (i) Background Magnetic-dipole (M1) excitation takes place in open-shell nuclei. In open-shell nuclei, the nuclear pairing correlation is expected to play a role. From the form of operator, this mode may provide the information on the coupled spin in medium. Our aim in this work To investigate the role of pairing correlation on M1. To introduce one case of “M1 sum rule” (its general version has not been established yet…), and its applicability to evaluatethe pairing effect.

  3. Introduction (ii) Matrix elements of M1 (up to the 1-body operator): Thus, M1 transition happens mainly between the LS-split levels, e.g. f7/2 f5/2 for Ca isotopes but except 40Ca.

  4. Three-body model (i) • We limit our targets to “shell-closed even-even core + 2N” systems in this work: e.g. 42Ca ≒ 40Ca + n + n. • The system consists of (i) a spherical, shell-closure, 0+ core and (ii) a pair of neutrons or protons. • Core is NOT active for excitation: we only discuss the M1 excitation of two valence nucleons. •  M1 from 0+ ground state (GS) to 1+ excited states is discussed. General coordinates: V + center-of-mass coordinates:

  5. Three-body model (ii) Hamiltonian: VC(Woods-Saxon) energy levels of the core-nucleon subsystem. vNNtwo-nucleon separation energy. schematic-density-dependent contact interaction, (2) Minnesota (finite-range) interaction,

  6. Three-body ver. of M1 sum rule Only 2 nucleons can be active: When 2n are coupled to JP=0+ at the initial state, possible combinations of (L12, S12) = (1,1) or (0,0) only. Thus, → Sum-rule value (SRV) of BM1(Ef) is related with the spin-triplet ratio in the initial state. +Spin-triplet ratio depends on the pairing strength. → M1 SRV can be used to evaluate the pairing in medium. Note: we discuss M1 up to the one-body-operator level in this work. Spin-triplet ratio

  7. Results for 42Ca BM1(Eγ; 0+ → 1+), Eγ= Ef− EGS Note: EGS= -S2n= -19.843 MeV in experimental data. Numerical SRV: • Sum-rule value of BM1(Eγ) is consistent to the S12=1 ratio in the GS. • BM1(Eγ) is sensitive to the pairing-interaction models, even when those are equivalently fitted to the GS energy. •  Low-lying M1 transition can provide a good reference to validate and optimize the pairing models.

  8. Results for sd-shell nuclei 16O+2n or 2p 18O, EGS(Exp.)= -12.188 MeV 18Ne, EGS(Exp.)= -4.523 MeV

  9. Relativistic Meanfield Cal. Refs: [1] D. Vretner et al., Phys. Rep. 409, 101-259 (2005); [2] N. Paar and P. Ring, Phys. Rev. C 67, 034312 (2003). Point-coupling Lagrangian: QRPA: • M1 occurs between LS-split levels. • Relativistic Meanfield (RMF) concludes the LS splitting naturally. • 　↓ • QRPA based on the RMF (Hartree+Bogoliubov) is the suitable method for the systematic M1 calculation.

  10. Result with RMF • Setting: • System = 42Ca • EDF = DDPC1(+ Pair.) • 20 HO Shells • Spherical • Result: • M1 sumrule value (SRV) • = 0.836 gs2 without pairing; • 0.634 gs2with pairing. • Note that SRV = 0.858 gs2(analytic) for no-pairing case. • BM1(E) value is consistent to the three-body model’s one. • Excitation energy depends on models. VS Three-body model result: Preliminary

  11. Conclusions • M1 transitions in C+2N systems are evaluated. The corresponding, case-limited version of sum rule is introduced. • Three-body model calculation shows the sensitivity of M1 to the pairing model.  M1 can be a good (i) probe for the pairing correlation in medium, and (ii)reference to optimize its model. • Relativistic HB + QRPA result is consistent to the three-body model’s one, except the excitation energy. • More systematic calculation with the RHB+QRPA, for other nuclei, where the experimental data are available. • Careful study on the pairing models. • Optimization of (relativistic) EDF parameters. • Meson-exchange-current effect, for which we need to take multi-body-terms of operator/interaction into account. Future works

  12. Funding This work was supported by the QuantiXLie Centre of Excellence, a project co-financed by the Croatian Government and European Union through theEuropean Regional Development Fund - the Competitiveness and CohesionOperational Program (Grant KK.01.1.1.01.0004). For more information please visit: http://bela.phy.hr/quantixlie/hr/ https://strukturnifondovi.hr/ The sole responsibility for the content of this presentation lies with the Faculty of Science, University of Zagreb. It does not necessarily reflect the opinion of the European Union. Co-financed by the European Union through the Eurpoean Regional Development Fund

  13. Backup

  14. IS-IV decomposition:

More Related