Correlation between neutron skin thickness and R np for neutron-rich nuclei

1. Correlation between neutron skin thickness and Rnp for neutron-rich nuclei 孙小艳 方德清 马余刚 蔡翔舟 陈金根 郭威 田文栋 王宏伟 曹喜光 傅瑶 周培 张国强 2010年07月25日

2. outline • Introduction • Analytic Method & Important Results • Summary and Conclusions 1

3. PART I Introduction Why are we interested in neutron skin thickness ? • The availability of high intensity radioactive beams facilitates the exploration of the nuclei far from stab-ility line. • Neutron-rich nucleus are considered to have a neutron skin thickness. • Experimental data on neutron skin thickness is important to the study of Nuclear physics and astrophysics. • Difficult to accurately determine the neutron skin thickness. • Find some experimental observables to extract the neutron skin thickness. . 2

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5. PART Ⅱ Analytic Method & Important Results Description of the model IQMD QMD Classical in essence. However, many important quantum features are included Reasonably including isospin degrees of freedom in the mean field ,two-bodycollision, and Pauli blocking Initialization Mean field Two-body collisions Pauli blocking 4

6. Each nucleon is represented by a coherent state of a Gaussian wave packet Through a Wigner transformation, the one-body phase space distribution function for N-distinguishable particles is given by: The propagation of nucleons under the self-consistently generated mean field is governed by Hamiltonian equations of motion: 5

7. (1). Initialization • The density of neutron and proton is different. • The Droplet Model: is the normalization constant. Ci is the half density radius of neutron or proton Ri is the equivalent sharp surface radius of neutron and proton. fi is introduced by us to adjust the diffuseness parameter. Monte carlo sampling method to get the initial coordinate of nucleons 6

8. The momentum distribution of nucleons is generated by • means of the local Fermi gas approximation: Monte carlo sampling method to get the initial momentum coordinate of nucleons • The binding energies and root mean square (rms) radii of the initial configuration for the colliding nuclei are required to be stable. 7

9. (2). Mean field α = −356 MeV, β = 303 MeV，γ = 1.17 8

10. (3). Coalescence model • relative momentum smaller than p0= 300 MeV/c • relative distance smaller than R0= 3.5 fm • then coalescence to one cluster (4). Rnp and neutron skin thicknessδnp Rnp=Yn/Yp Yn : yield of neutrons Yp : yield of protons 9

11. Important Results The collision processes of some Ca and Ni isotopes with 12C target at 50AMeV are simulated using the IQMD model. The evolution time dependence of Rnp for 50Ca+12C at 50AMeV Rnp is stable after 150 fm/c 10

12. Strong correlation between neutron skin thickness and Rnp for 54Ca at peripheral collision 11

13. Different range of kinetic energy to see the correlation between neutron skin thickness and Rnp for 54Ca ，stronger correlation for Ken>40MeV 12

14. Correlation between neutron skin thickness and Rnp for 50 52 54 56 Ca and 60 62 64 66 68 70 Ni Physics letter B 682(2010)396-400 13

15. PART III Summary & Conclusion We have calculated Rnp from some Ni and Ca isotopes induced reactions using IQMD, the results show that Rnphas strong correlation with neutron skin thickness δnp Rnp may be used as an experimental observable to extract δnp for neutron-rich nuclei 14

16. Thank You 15