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Chang Ho Hyun Daegu University Work with S.-I. Ando (Daegu) Y.-H. Song (South Carolina)

Polarization of neutron in photodisintegration of deuteron at low energies [Phys. Rev. C 83, 064002 (2011)]. Chang Ho Hyun Daegu University Work with S.-I. Ando (Daegu) Y.-H. Song (South Carolina) K. Kubodera (South Carolina). APFB2011, Seoul, Korea, August 22-26. Outline Motivation

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Chang Ho Hyun Daegu University Work with S.-I. Ando (Daegu) Y.-H. Song (South Carolina)

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  1. Polarization ofneutron in photodisintegration of deuteron at low energies [Phys. Rev. C 83, 064002 (2011)] Chang Ho Hyun Daegu University Work with S.-I. Ando (Daegu) Y.-H. Song (South Carolina) K. Kubodera (South Carolina) APFB2011, Seoul, Korea, August 22-26

  2. Outline • Motivation • Formalism • Spin polarization P’y • Results • Conclusion

  3. Motivation • NN force well understood at Elab ≤ 300 MeV • Nevertheless many discrepancies in the polarization observables • Puzzles with spin • - P’y in deuteron photo-disintegration • - Ay puzzle in neutron-deuteron scattering • Spin is still an open problem in few-body systems

  4. Spin polarization P’y • - Experiments: 1961-1983 (John61, Jewell65, Nath72, Holt83) • - Jewell65 Jewell et al., PR 139, B71 (1965)

  5. Need to investigate the problem with modern theories • - Effective field theories (EFTs) provide proper tools • Our choice: Pionless EFT with dibaryon fields

  6. Formalism • Pionless theory • - Integrate out the pion • - NN contact interactions • - Low energy constants determined by low-energy data • Dibaryon fields • - Nucleon bubbles summed infinitely, the deuteron pole reproduced successfully • - Ensure fast convergence with only a few leading terms

  7. Lagrangians • si, ti : dibaryon fields in 1S0 and 3S1 states, respectively • Bi : external photon fields

  8. Low energy constants • ys, yt: dNN coupling constants. Fitted to effective range parameters • L1, L2 : ddV coupling constants. Fitted to np capture cross section at threshold and deuteron magnetic moment • Total np capture cross section

  9. Spin polarization P’y • Definition z’ g y’ n p s+,-(q) : differential cross section with parallel and anti-parallel neutron spin P’y non-zero by the interference of even and odd transition amplitudes

  10. Amplitudes and cross sections • Feynman diagrams • Amplitudes

  11. Cross section for unpolarized neutron • Projection operator for the neutron spin

  12. Cross section for polarized neutron • Result for P’y

  13. Results • Differential cross section of unpolarized neutron Eg = 19.8MeV De Pascale et al. PRC 32, 1830 (1985) Modern potential R. Schiavilla, PRC2005 Our work

  14. P’y at Eg = 2.75 MeV Modern potential R. Schiavilla, PRC2005 Our work

  15. P’y at q = 45

  16. P’y at q = 90

  17. Conclusion • What is the correct answer? • Experiment side • - Large errors • - Data do not converge (q = 90) • - New measurements necessary • Theory side • - SNPA results discrepant from pionless EFT • - Systematic investigation at higher orders : e.g. D-wave contribution

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