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基于 RIBLL 测量对称能 —— 同位旋标度法和同质异位素产额比方法的对比

HIRFL-RIBLL 合作体第 2 次会议. 基于 RIBLL 测量对称能 —— 同位旋标度法和同质异位素产额比方法的对比. 马春旺 Email: machunwang@126.com 王闪闪 , 张艳丽 河南师范大学物理学系. 1.Backgrounds. Nuclear symmetry energy Induced by the difference between neutron and proton (numbers/density distributions); Temperature- and density- dependent;

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基于 RIBLL 测量对称能 —— 同位旋标度法和同质异位素产额比方法的对比

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  1. HIRFL-RIBLL合作体第2次会议 基于 RIBLL 测量对称能 ——同位旋标度法和同质异位素产额比方法的对比 马春旺 Email: machunwang@126.com 王闪闪,张艳丽 河南师范大学物理学系

  2. 1.Backgrounds • Nuclear symmetry energy • Induced by the difference between neutron and proton (numbers/density distributions); • Temperature- and density- dependent; • Various of observables promoted in theory and exp.; no consistent results obtained; • Important parameter in nucl. Phys., nucl astrophys etc.; • Still an open question. • Heavy-ion reactions (HICs) • (RIB) Provide the lab of sub-saturate and supra-saturate nuclear matters • High temperature of primary fragment, relatively low temperature of final fragment—decrease of temperature in secondary decay process • Finite neutron-rich isotopes measured with some low temperature, which relates to sub-saturate nuclear matter • Difficult to understand the symmetry energy of neutron-rich nucleus

  3. Pigmy/Giant resonances • Nucleon optical potential 1.Backgrounds Probes New choice: Isobaric methods B.A. Li/L.W. Chen/C.M. Ko Phys. Rep. 464, 113(2008)

  4. 1.Backgrounds • Isotopic yields in HICs • Fragments: measured after the secondary decay process (after particle emitting ceases ) • A low but nonzero temperature; • Yields reflect its free energy (due to temperature) and the chemical property of the colliding source; • Free energy: alter the terms contributing to the binding energy B(T); • Chemical property of the colliding source– the symmetry energy of the source; • Important for the search of the very neutron-rich nucleus near the dripline. • From fragments-- probes to symmetry energy in HICs • Isotopic scaling—symmetry energy of the source (T and density depended) • Neutron-skin thickness– indirect probes for symmetry energy • Isobaric ratio—symmetry energy of neutron-rich fragments at low T; • From fragments-- probes to temperature in HICs • Isotopic temperatures (Albergo thermometer) • Excitation energy, kinetic energy spectrum, thermal energy, etc. • Isobaric ratio

  5. P r e l i m i n a r y similar results as that in Eur. Phys. J. A 48(2012) 78 1. backgrounds • 利用isobaric yield ratio方法获得的HIC中丰中子核的对称能系数温度比

  6. 与发射源性质 如对称能等有关 余核(簇团) 自由能 中子 化学势 质子 化学势 2. Theoretical analysis • 巨正则近似下,重离子核反应中余核产额 • 利用余核产额研究反应系统中核物质对称能的方法 • 同位旋标度法(同位素产额比isoscaling) • 同质异位素产额比法

  7. 2.1Methods: isoscaling • isoscaling • Relating the yields of fragments to the source property • n/p fixed source, μnandμp vary slowly with the size of source; temperature in reactions to be the same (same fragment) • Isotopic ratio (α) to μn, and isotoinc ratio(β) to μp , difference between αand βto Csym. • Csym: temperature dependence • Secondary decay effect Different type of models; Different type of reactions PRL85,716(2000);JPG34,2173(2007);PRC81,064613(2010);PRC72,064603(2005);PRC78,014605(2008);PRC80,044606(2009);PRC73,044601(2006);PRC68,051601(R)(2003);EPJA30,129(2006);PRC64,054615(2001);PRC65,044610(2002

  8. ? ? ? 2.2 Isobaric ratio difference method • 类似isoscaling方法,在两个炮弹中子丰度不同的反应体系中进行研究. • 在单个反应中,定义同质异位素产额比 • I=N-Z,为中子剩余度 • 取对数,有

  9. 在两个反应中,取同质异位素产额比的差 • △F消掉,同isoscaling一样,不用测量非零温度余核的结合能(目前无法测量)

  10. 3. Results and discussion Isoscaling results

  11. 3. Results and discussion • 140A MeV 48Ca/40Ca+9Be • 趋势相同,同I,A大时有差别 • I=0和1时,基本相同 • A小的部分,均构成平台

  12. 3. Results and discussion • 140A MeV 58Ni/64Ni +9Be • 与48,40Ca反应中结果类似, • 趋势相同,同I,A大时有差别 • I=0和1时,基本相同 • A小的部分,均构成平台

  13. 3. Results and discussion • 140A MeV 58Ni/40Ca +9Be • 趋势相同, • 二者结果相差较小 • A小的部分,均构成平台

  14. 3. Results and discussion • 140A MeV 48Ca/64Ni +9Be • I<3时,在A较大部分有一定的差别 • I≥3时,结果差别不大

  15. result and discussion • different targets • 相反的趋势 • isospin diffusion? • need carefully check

  16. 3. Results and discussion • 简单讨论 • 原理上,△lnR21与isoscaling中α-β相等 • 结果中所示的差别来源猜测 • 周边和中心反应区域的温度不同 • IYR方法方法中,T仅与isobaric fragments有关且可变,而isoscaling中,T是统一量. • 由于中心反应产物温度大于周边反应产物,导致IYR方法得到的△lnR21> (α-β) • 可能的意义: • 平台高度与密度的关系 • α-β与对称能相关,在IYR方法中, △lnR21偏大,可能改进目前人们关于核物质状态方程的知识 • 丰中子核物质对称能随温度和密度研究

  17. 4. 基于Ribll实验开展研究 • 目前已有实验中,所测量的余核机制混杂,Proj-Like,Targ.-Like等不加区分. • ~35A MeV40,48Ca+12C 丰中子核引起核反应产物测量 • 区分碎片的来源PL,TL等并研究其对物理结果的影响. • 相关的理论模拟(AMD等动力学模型分析)

  18. Thank you!

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