60 A GeV16O原子核在核乳胶中的电磁离解

对60 A GeV16O在原子核乳胶中的电磁离解现象首次进行了高统计的研究,得到电磁离解截面随束流能量的增加而增加,射弹碎片电荷分布和200 A GeV16O在乳胶中电磁离解的电荷分布一致,但电荷为3≤Z≤5的射弹碎片的发射概率低于200 A GeV能区,这些特点和Weiszacker和Williams的经典电磁理论模型计算结果一致.60 A GeV16O电磁离解下各反应道出现的概率和200 A GeV能区结果基本一致,但同14.6 A GeV能区的结果不同,在60 A GeV能区16O电磁离解主要是由电偶及电四激发引起的巨偶极和巨四极共振及准氘核效应过程所致,这一点可以通过电磁离解下质子的多重数分布得到定性解释.电磁离解下α射弹碎片的分布同非弹核作用下α碎片的分布规律不同,说明α碎片的产生机制不同.     

60AGeV 16O诱发乳胶核反应α射弹碎片发射研究

对60AGeV 16 O诱发乳胶核反应射弹α碎片的发射进行了研究,得到α射弹碎片多重数分布服从KNO标度无关性. 在边缘作用下,α射弹碎片的产生与靶核碎片的产生存在线性关联,靶核碎片平均多重数随α射弹碎片数的增加线性减小,它可以很好地利用核作用几何模型来解释.     

高能原子核碎裂中的矩关联

本文用瓜分客体的方法，得到了＾１６Ｏ和＾３２Ｓ碎裂中碎片电荷分布的条件矩、结果表明条件矩间呈对数关联，且对关联行为本身来说，电磁离解和核反应相应的结果类似，氧核与硫核相应的结果类似。计算结果与３．７和２００ＧｅＶ／ｕ＾１６Ｏ及２００ＧｅＶ／ｕ＾３２Ｓ与核乳胶作用的实验数据符合。     

3.7 A GeV 16O与乳胶作用相对论性α粒子的双源发射

对3.7 A GeV 16O与原子核乳胶作用α射弹碎片的发射进行了研究, 发现α射弹碎片的角分布不能用单一的旁观体-反应体模型来解释，所以假设α射弹碎片来源于两个温度不同的发射源。     

60A GeV16O诱发乳胶核反应慢粒子产生研究

对60AGeV ¹⁶O诱发乳胶核反应靶核碎片多重数分布及其关联进行了实验研究,并与FRITOF1.7加级联机制模型和DTUNUC 2.0模型计算结果进行了比较.     

60AGeV 16 O诱发乳胶核反应α射弹碎片发射研究

对60AGeV^16O诱发乳胶核反应射弹α碎片的发射进行了研究，得到α射弹碎片多重数分布服从KNO标度无关性。在边缘作用下，α射弹碎片的产生与靶核碎片的产生存在线性关联，靶核碎片平均多重数随α射弹碎片数的增加线性减小，它可以很好地利用核作用几何模型来解释。     

16O+238U垒下熔合裂变碎片角分布

利用云母核径迹探测器测量了轰击能量从73.7—93.4MeV的¹⁶O+²³⁸U反应的裂变截面和碎片角分布.用考虑了核静态形变的Wong模型很好地重现了裂变激发函数,由此抽取了复合核的自旋分布.同时,利用裂变鞍点过渡态理论以抽取的自旋分布计算了裂变碎片角分布,表明碎片各向异性实验值大于理论值.此外实验揭示出,在低能区碎片各向异性随入射能量变化的走向不同于以前的测量结果.     

垒下16O+232Th裂变碎片角关联模拟

使用Monte-Carlo模拟计算了垒下¹⁶O+²³²Th系统转移裂变和复合核裂变碎片角分布及角关联.转移过程、熔合过程和裂变过程分别用半经典模型、耦合道模型及鞍点过渡态统计模型进行模拟.考虑了各物理量分布产生的运动学效应及裂前中子发射和裂后碎片粒子蒸发对碎片角分布及角关联的影响.模拟结果和实验测量的分布相一致.使用折叠角技术借助Monte-Carlo模拟区分转移裂变和复合核裂变是可能的.考虑了转移裂变和裂前中子发射的影响,复合核裂变碎片角分布各向异性异常仍然存在.     

16O+232Th垒下全熔合裂变

利用裂变碎片的折叠角分布,从实验上实现了全熔合裂变和转移跟随裂变两种成份的区分.在此基础上测量了质心系能量72.61至80.11MeV ¹⁶O+²³²Th全熔合裂变截面和碎片角分布.包含靶核静态形变效应的耦合道模型计算与实验激发曲线一致.然而,裂变统计理论无法解释实验上观察到的全熔合裂变碎片角分布.而鞍点模型与断点模型的理论预言有较明显的差别.     

相对论性16O与乳胶碰撞产生的He碎片动量分布宽度的分析

本文探讨了在2GeV/n～200GeV/N能区,相对论性¹⁶O原子核碎裂产生的He碎片动量分布宽度随其多重数的减小而增加的实验现象.研究表明随He碎片多重数的减小,弹核旁观体所获得的表面激发能增加,从而导致了He碎片的动量分布宽度增加.分析表明正是由于弹核旁观体在不同能量下获得了相同的激发能从而表现出在该能区产生的He碎片多重数分布与弹核能量无关的极限碎裂特征.     

Electromagnetic dissociation of 3.7 A GeV^16O in nuclear emulsion

The electromagnetic dissociation (ED) of 3.7 A GeV {}^{16}O in nuclear emulsion is investigated with high statistics. It is found that the electromagnetically dissociated cross section increases with increasing beam energy, the charge distribution of projectile fragments is the same as the results at 60 and 200 A GeV, and the production probability of projectile fragments with charge 3≤Z≤5 is less than that of the other projectile fragments. These results can be well explained by use of Weizsacker and Williams method for calculating the ED contributions. The percentile abundance of various decay modes for ED at 3.7 A GeV is close to the result at 60 and 200 A GeV, but it is different from the result at 14.6 A GeV. The ED of 3.7 A GeV is mainly caused by the giant dipole and quadrupole resonance of E1 and E2, which can be qualitatively explained by the multiplicity distribution of projectile proton in ED. The multiplicity distribution of the α fragments in ED and nuclear events have different functional forms. This difference may be a consequence of the different reaction mechanism involved.     

Fragmentation of ^16O nuclei in nuclear emulsion

We present the topology of 16O fragmentation at 60A GeV in reactions with emulsion nuclei.We discuss the multiplicity distributions of projectile fragments.charged secondaries and their dependence on the target residues.     

Investigation of the mean free path of projectile fragments produced in 16O－Em collision at 60 A GeV

Results are presented for an investigation of the mean free path of projectile fragments with charge 3≤Z≤8, produced by 60 A GeV {}^{16}O in nuclear emulsion. No dependence of mean free path on the distance from the point of the fragment emission is observed and our result is consistent with the nonexistence of anomalons.     

INTERACTION MEAN FREE PATH OF He PROJECTILE FRAGMENTS FROM 16O-EM COLLISION AT 60 A GeV

The interaction mean free path of He projectile fragments, produced by the collisions of ^{16O at 60 A GeV in a nuclear emulsion, has been investigated. In the present analysis, 1555 He projectile fragments, giving rise to 320 secondary interactions, have been used. At a level of 3% a very weak signal of anomalons is observed, which comes mainly from the 3×He channel.}     

Production of helium projectile fragments in {16O－emulsion interactions at 4.5 A GeV/c

The measurements of partial production cross sections of the multiple helium projectile fragments emitted at 4.5 A GeV/c {}^{16}O－Em interactions are reported. We have studied the production rate of helium projectile fragments due to fragmentation of {}^{16}O ions and compared it with that obtained from different projectiles at various energies. The dependence of on the mass number of the incident beams is formulated. The multiplicity distributions of the helium fragments produced in {}^{16}O－Em interactions at different energies exhibit Koba－Nielson－Olesen (KNO) scaling. The correlation of helium projectile fragments and target fragments is also investigated and it is found that the average of target fragments is increased with the decrease of the number of helium fragments in peripheral interactions.     

Fragmentation in ^16 O-emulsion interactions at 3.7 A GeV

The topology of ¹⁶O fragmentation at 3.7 A GeV in reactions with emulsion nuclei is presented. The multiplicity distributions of projectile fragments,charged secondaries and their dependences on the projectile residues are discussed.     

Isotopic production cross sections of fragmentation residues produced by 18O ions on a carbon target near 260 MeV/nucleon

The isotopic cross sections of residual nuclei produced in fragmentation reactions of ¹⁸O projectiles impinging on a carbon target at energies near 260 MeV/nucleon were measured at the HIRFL facility in Lanzhou (China). A full identification of atomic and mass numbers of fragments was achieved from the determination of their magnetic rigidity, energy loss, and time of flight. The production cross sections for a dozen of nitrogen, carbon, and boron isotopes were determined with uncertainties below 30% for most of the cases. The obtained cross sections for N and B isotopes show a rather good agreement with previous experimental data obtained with different projectile energies. The cross sections for some C isotopes seem to exhibit a dependence on the projectile energy. A comparison of the data and several theoretical model calculations are presented.