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Exciting the GDR in ( p,n ) reactions: A new Approach for Probing the Neutron Skin

Exciting the GDR in ( p,n ) reactions: A new Approach for Probing the Neutron Skin. A. Krasznahorkay, ATOMKI, Debrecen for the R3B and EXL collaborations. Constraining the symmetry energy. Furnstahl, Nucl. Phys. A706 (2002) 85. The symmetry energy in nuclear matter.

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Exciting the GDR in ( p,n ) reactions: A new Approach for Probing the Neutron Skin

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  1. Exciting the GDR in (p,n) reactions: A new Approach for Probing the Neutron Skin A. Krasznahorkay, ATOMKI, Debrecen for the R3B and EXL collaborations

  2. Constraining the symmetry energy Furnstahl, Nucl. Phys. A706 (2002) 85

  3. The symmetry energy in nuclear matter

  4. Density dependence of the symmetry energy

  5. Workshops in 2010 • Asy-EOS-2010, "International Workshop on Nuclear Symmetry Energy at Medium Energies", May 21 to May 24, 2010, in the town Noto (SR), Italy. • International symposium on Nuclear Symmetry Energy, July 26 to July 28, 2010 at RIKEN, Wako, Japan.

  6. Sum rule for the SDR strength Neutron-skin thickness Bohr, Mottelsson Nuclear Structure (1969) Vol. 2 A. Krasznahorkay et al., Phys. Rev. Lett. 82 (1999) 3216.

  7. Problems with the SDR method • Quenching of the SDR is not known • Normalization of the strength is not solved • Spin-Dipole Res.S[r(i)x(i)]t3(i) • IAS Sr(i)t3(i) • The QFC background is not precisely defined

  8. The previous sum rule is valid also for the GDR if it excited in (p,n) reaction !!! • (actually the analog of the GDR is ecited)

  9. Advantages of the proposedGDR method • Very little quenching, and it is precisely known for the whole nuclear chart • Normalisation can be more precise • GDR Sr(i)t3(i) => DL =1 • IAS Sr(i)t3(i) => DL =0 • In coincidence with γ-decay no QFC background is expected

  10. Excitation with strong interaction V(q=0) (MeVfm3) voc v v v

  11. Neutron energy spectra and differential cross sections from (p,n) reaction(S. Nishihara et a., Phys. Lett. B 160 (1985) 369

  12. Ground-stateγ-decay of the GDR

  13. Reaction kinematics

  14. Schematic layout of the setup

  15. Geometrical arrangement

  16. Efficiency for neutrons

  17. New proposal for G-PAC Constraining the symmetry energy of the EoS by precise neutron-skin thickness measurements We propose to study the absolute, model independent neutron-skin thicknesses of208Pb, 116Sn and 124Sn isotopes by measuring the strength of the isovector giant dipoleresonance (IVGDR) excited in (p,n) reactions using inverse kinematics in order to constrainthe symmetry energy of the EoS. We request 10 days of beam time for these investigations.

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