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基于量子分子动力学模型, 以核子轫致辐射光子为探针, 系统研究了高动量分布(HMT)对核反应系统的影响, 并探讨了这种影响与入射能量、碰撞参数及同位旋相关核子-核子碰撞截面的关系. 研究结果表明: 在入射能量为50 MeV/u时, 从轻到重的反应系统, 含HMT的系统在高能区的光子密度均显著高于无HMT的系统, 而在低能区两者差异不明显. 此外, 在对心碰撞中光子能量改变现象随入射能量的增加而增强, 并在E = 150 MeV/u时达到峰值. 这一由HMT引起的能量移动现象在碰撞参数b = 0—6 fm范围内普遍存在. 进一步分析表明, 同位旋相关核子-核子碰撞截面的引入会改变系统的碰撞概率, 而HMT通过影响核子间相互作用进一步调制了这一过程. 综上所述, 高动量分布对核反应系统具有重要影响, 其效应与入射能量和同位旋相关核子-核子碰撞截面密切相关.In this work, semi-classical quantum molecular dynamics is used to investigate the influence of high momentum distribution on nuclear reaction systems by using photons produced by nucleon bremsstrahlung as indicators. The research examines the relationship between this influence and the incident energy, collision parameters, and the differences in isotopic spin cross-sections. Under the condition of a 20% high-momentum distribution and ensuring the conservation of nuclear energy, a system different from traditional configurations is constructed by sampling neutrons and protons using the Monte Carlo method, with the selected nucleons exhibiting characteristics of high-momentum nucleons. The influence of high-momentum distribution within the nucleus on bremsstrahlung photons is analyzed through the collision results of heavy ions in nuclear systems spanning from light to heavy species. The results indicate that, at an incident energy value of 50 MeV/u, the collision system studied in this work exhibits higher photon density in the high-energy region of high momentum distribution system than traditional system for nuclear systems ranging from light-mass system (18O+18O), lower-mass system (46Ca+46Ca), and medium-mass system (86Kr+86Sr) to heavy-mass system (124Sn+124Sn), than those, while there is no significant difference in photon density in the low-energy region. At a collision parameter b = 0 fm, the energy shift phenomenon of photons produced by collisions becomes more pronounced with the increase of incident energy, peaking at E = 150 MeV/u. This energy transfer phenomenon induced by high momentum distribution typically exists within the collision parameter range from b = 0 fm to b = 6 fm. When considering isotopic spin cross-sections, high momentum distribution can affect the collision probability of the system. Therefore, high momentum distribution has a significant influence on nuclear reaction system, closely related to incident energy and isotopic spin cross-section.
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Keywords:
- high-momentum distribution /
- heavy-ion collision /
- spectrum /
- isospin effect
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图 2 不同质量核系统在中心碰撞中产生的光子能量分布, 分别考虑(HM)和不考虑高动量分布(NH)的情况
Fig. 2. Photon energy distribution in central collisions of nuclear systems with different masses, considering and not considering high-momentum distributions.
图 3 较轻质量核系统和中等质量核系统中高动量分布系统与常规系统的光子密度比与光子能量的关系
Fig. 3. Relationship between the photon density ratio and photon energy for high-momentum distribution systems versus conventional systems in lower-mass and medium-mass nuclear systems.
图 4 中等质量核系统在中心碰撞中产生的光子相对数量与入射能量的关系
Fig. 4. Relationship between the relative number of photons produced in central collisions and the incident energy for a medium-mass nuclear system.
图 5 中等质量核系统碰撞参数与碰撞产生的光子相对数量的关系
Fig. 5. Relationship between the collision parameter and the relative number of photons produced in collisions for a medium-mass nuclear system.
图 6 不同中质量和较轻质量核系统在中心碰撞中产生的低能和高能光子相对数量的关系, 分别考虑和不考虑高动量分布的情况
Fig. 6. Relationship between the relative number of low-energy and high-energy photons produced in central collisions, considering and not considering high-momentum distribution, across different medium-mass and lower-mass nuclear systems.
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