本文選題：對稱能 + 高密行為　； 參考：《蘭州大學(xué)》2016年博士論文

【摘要】：非對稱核物質(zhì)狀態(tài)方程(特別是對稱能的高密行為)的研究是當(dāng)前核物理領(lǐng)域的熱點(diǎn)之一,這一研究對于認(rèn)識和理解核物理與核天體物理中許多物理問題和物理現(xiàn)象至關(guān)重要。重離子碰撞是目前實(shí)驗(yàn)室內(nèi)可以形成高密非對稱核物質(zhì)從而用于研究對稱能高密行為的唯一手段。由于實(shí)驗(yàn)上不能直接測量對稱能,人們需要利用輸運(yùn)理論模型模擬重離子碰撞過程并與相應(yīng)的實(shí)驗(yàn)觀測量進(jìn)行比較來間接提取對稱能密度依賴性的相關(guān)信息。目前,中國、美國、德國、日本等國家的各大重離子實(shí)驗(yàn)室都將非對稱核物質(zhì)性質(zhì)以及對稱能高密行為的研究作為主要的物理目標(biāo)。本論文在同位旋依賴的Boltzmann-Uehling-Uhlenbeck(IBUU)模型和極端相對論量子分子動力學(xué)(UrQMD)模型理論框架內(nèi),通過系統(tǒng)模擬中能重離子碰撞過程,研究了對稱能的各種靈敏觀測量,得到了一些有價值的結(jié)果,主要包括:研究并指出了π-/π+比、自由核子發(fā)射n/p比、質(zhì)子和中子的集體流、中子-質(zhì)子微分橫向流等常用的對稱能敏感觀測量的模型依賴性;研究了高密對稱能對核子的同位旋相分化的影響,提出高動能核子的正常和反常同位旋相分化可以作為模型無關(guān)的對稱能高密行為的定性探針;討論了介質(zhì)中核子-核子彈性散射截面對域下π介子發(fā)射的影響,結(jié)果表明:具有相同質(zhì)量數(shù)的豐中子系統(tǒng)和缺中子系統(tǒng)的π-/π+的雙比可以消除介質(zhì)中核子-核子彈性散射截面效應(yīng),而保留對稱能效應(yīng);研究了π勢對重離子碰撞中π介子發(fā)射的影響,結(jié)果表明:在較低束流能量下,由于π勢的作用,對稱能對π-/π+比的影響會減小;還進(jìn)一步研究了?共振態(tài)勢對π-/π+比和預(yù)平衡發(fā)射核子n/p比的影響,結(jié)果表明:?共振態(tài)勢對預(yù)平衡發(fā)射核子n/p比幾乎沒有影響,而對π-/π+比有輕微的影響,而且,在采用軟的對稱能時,可以用核子的同位旋標(biāo)量勢代替?共振態(tài)勢,從而避免??π反應(yīng)道的能量不守恒問題。
[Abstract]:The study of asymmetric nuclear matter equation of state (especially the high density behavior of symmetric energy) is one of the hotspots in the field of nuclear physics. This research is very important for understanding and understanding many physical problems and phenomena in nuclear physics and nuclear astrophysics. Heavy ion collision is the only way to study symmetric energy and high density behavior in laboratory. Because the symmetry energy can not be measured directly in the experiment, it is necessary to simulate the heavy ion collision process by using the transport theory model and compare it with the corresponding experimental observations to extract indirectly the relevant information of the symmetry energy density dependence. At present, the major heavy ion laboratories in China, the United States, Germany, Japan and other countries have made the study of asymmetric nuclear matter properties and the high density behavior of symmetric energy as the main physical targets. Within the framework of the isospin dependent Boltzmann-Uehling-Uhlenbecking-IBUUU model and the ultra-relativistic quantum molecular dynamics (QMD) model, various sensitive measurements of symmetric energy are studied through the systematic simulation of energy heavy ion collisions. Some valuable results are obtained, including: the model dependence of the commonly used symmetric energy sensitive observations, such as 蟺-/ 蟺 ratio, free nucleon emission n / p ratio, collective flow of protons and neutrons, neutron differential transverse currents, etc. The effect of high density symmetric energy on the isospin differentiation of nucleon is studied. It is suggested that the normal and abnormal isospin differentiation of high kinetic energy nucleon can be used as a qualitative probe for the model-independent symmetric energy high density behavior. The effect of the nucleon-nucleon elastic cross section on the 蟺 meson emission in the medium is discussed. The results show that the 蟺-/ 蟺 double ratio of the rich and missing subsystems with the same mass number can eliminate the nucleon-nucleon elastic cross section effect in the medium, but retain the symmetric energy effect. The effect of 蟺 potential on 蟺 -meson emission in heavy ion collisions is studied. The results show that the effect of symmetry energy on 蟺-/ 蟺 ratio is reduced at lower beam energy, and the effect of symmetry energy on 蟺-/ 蟺 ratio is further studied. The effect of the resonance state on the 蟺-/ 蟺 ratio and the n / p ratio of the pre-equilibrium emission nucleon is obtained. The resonance state has little effect on the n / p ratio of the pre equilibrium emission nucleon, but has a slight effect on the 蟺-/ 蟺 ratio. Moreover, the isospin scalar potential of the nucleon can be replaced by the soft symmetric energy. Resonance state, thus avoiding the energy nonconservation of pion reaction channel.
【學(xué)位授予單位】：蘭州大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2016
【分類號】：O571.6

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相關(guān)期刊論文 前2條

1 ZHANG Yingxun;LI Zhuxia;ZHAO Kai;LIU Hang;TSANG M B;;Constraints on symmetry energy and n/p effective mass splitting with improved quantum molecular dynamics model[J];Nuclear Science and Techniques;2013年05期

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本文編號：1820252