Reaction Cross Sections and Nucleon Density Distributions of Light Nuclei. Maya Takechi

Transcription

1 Reaction Cross Sections and Nucleon Density Distributions of Light Nuclei Maya Takechi

2 Collaborators

3 Introduction Sizes of Unstable Nuclei? ~ Measurements of σ R ~ σ R σ tot σ el ρ r ρ Glauber Calculation (OLA) r At Intermediate Energies Nucleon Density Distribution! ρ r

4 Study of Density Distribution through Glauber Calculation ρ σr σ R = σr can be uniquely calculated by 3 quantities ρ(r) db 1 exp d 2 r Radius contributing to the R i,j ρ P ρ T σ NN Glauber Calculation (Optical Limit and Zero-Range Approximations of Glauber Theory) P σ NN ( E)ρ i T z (r)ρz j (r - b) Target Density Energy High, σnn Small narrow σ Projectile Density NN total cross section Energy Low, σnn Large wide σnn (E ) Problem σ σ Glauber Calculation underestimates σr at Intermediate Energies Investigation Measurements of σr for 12 C, 11 Be

5 Transmission Method N1 : Incident Beam N2 : Non-reacting Events σ R = 1 t ln N 2 N 1

6 Result of σr for 12 C Comparison with Glauber Calculation OLA, Zero-Range 12 C + 9 Be 12 C + 12 C 12 C + 27 Al Expt. > Calc.

7 Improvement of Galuber Calculation ~ 3 Points ~ Neglect of Internal Motion of Nucleons Take into Account Fermi Motion Effect Optical Limit Approximation Take into Account Multiple Scattering Effect (Important for Halo Nucleus.) B. Abu-Ibrahim and Y. Suzuki PRC 2 (2000) Zero - Range Approximation Finite Range Calculation

8 Modifications for Galuber Calculation ~ 3 Points ~ Neglect of Internal Motion of Nucleons Optical Limit Approximation p nucleon Eproj Take into Account Fermi Motion Effect FM σ NN σ free NN σ NN FM (E nucleon ) = Zero - Range Approximation + dp nucleon σ free NN (p nucleon ) P(p nucleon )

9 Modified Glauber Calculation and Data of 12 C 12 C + 9 Be 12 C + 12 C 12 C + 27 Al Modified Glauber Calculation Successfully Reproduce our Data

10 Comparison with the Data for Unstable Nuclei 11 Be, B Be + 9 Be, 12 C, and 27 Al B KI00 (HF + HF) r (fm) 11 Be 11 Be B B + Be, C, Al r (fm) HF Densities H. Sagawa and H. Toki, J. Phys. G 13, 453 (197). and Private Communications M. Fukuda et al., Nucl. Phys. A 5 (1999) 209. I. Tanihata et al., Phys. Lett. 20B (19) 592 B. Blank et al., Nucl. Phys. A 24 (1997) 242. M. Obuti et al., Nucl. Phys. A09 (199) 74.

11 Modified Glauber Calculation successfully reproduces σ R for various nuclei including halo nuclei. The Problem (σ R(calc.) < σ (RExpt.) ) has been solved. Now we can deduce nucleon density distributions of unstable nuclei We have already investigated several nuclei. He, He, and Li

12 Skin and Halo Nuclei He, He so-called Neutron-Skin Nuclei He? and Li Cluster Structure He? Weakly Bound Deuteron 1.47 MeV It is not Clear whether there is Halo Tail Halo or Skin?

13 How to Deduce Nucleon Density Distribution ρ (r) ρ (r) : Model Density Change model assumption Parameter! 2 4 r (fm) Glauber Calculation Feed Back Calculation Compare Again!!! σ R(Calc.) Compare σ R(Expt.)

14 Cross Section Calculation He on Be, C, Al He He on Be, C, Al Nucl. Phys. A 712 (2002)

15 Cross Section Calculation He on Be, C, Al He He on Be, C, Al Nucl. Phys. A 712 (2002) He Nucl. Phys. A 712 (2002)

16 Result for Li r (fm)

17 Summary We precisely measured reaction cross sections for 12 C and 11 Be at intermediate energies to investigate the applicability of Glauber Calculation to the intermediate energy region. By taking into account Fermi-Motion Effect, Multiple Scattering Effect, and Finite Range Effect, Glauber Calculation successfully reproduce the data. Using Modified Glauber Calculation, investigations of nucleon density distributions for various nuclei will be carried out.