Direct photon produced from first proton-neutron ($p\text{\ensuremath{-}}n$) collision during the early stage of heavy ion reaction is a sensitive probe to reflect energy and momentum distribution of nucleons. In this work, we embedded the hard photon production channel in an extended quantum molecular dynamics (EQMD) model, and took the direct photon as a possible probe to improve namely the Fermi motion in the EQMD model. A possible scheme is offered to handle the dynamical wave packet width within incoherent bremsstrahlung process. Direct photons calculated by our modified EQMD were compared with data of $^{14}\mathrm{N}+^{12}\mathrm{C}$ at beam energies $E/A$ = 20, 30, and 40 MeV, and it is found that the yield, inverse slope, and angular distribution of direct photons could be reasonably reproduced. In addition, asymmetric reaction systems of $^{4}\mathrm{He} +$ C and $^{4}\mathrm{He} +$ Zn at $E/A$ = 53 MeV are also simulated in this work. It is found that the symmetric angular distribution in the nucleon-nucleon ($N\text{\ensuremath{-}}N$) center-of-mass (c.m.) frame and the velocity of the $\ensuremath{\gamma}$-emission source can be reasonably obtained from our method although there is some quantitative difference.

中文翻译：

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直接光子发射和动态波包在扩展量子分子动力学模型中的影响

重离子反应早期第一次质子-中子($p\text{\ensuremath{-}}n$)碰撞产生的直接光子是反映核子能量和动量分布的敏感探针。在这项工作中，我们将硬光子产生通道嵌入到扩展量子分子动力学（EQMD）模型中，并将直接光子作为可能的探针来改进 EQMD 模型中的费米运动。提供了一种可能的方案来处理非相干韧致辐射过程中的动态波包宽度。将我们修改后的 EQMD 计算的直接光子与束能量 $E/A$ = 20、30 和 40 MeV 下 $^{14}\mathrm{N}+^{12}\mathrm{C}$ 的数据进行比较，并且发现可以合理地再现直接光子的产率、反斜率和角度分布。此外，在这项工作中还模拟了 $^{4}\mathrm{He} +$ C 和 $^{4}\mathrm{He} +$ Zn 在 $E/A$ = 53 MeV 的不对称反应系统。发现nucleon-nucleon($N\text{\ensuremath{-}}N$)质心(cm)坐标系中的对称角分布和$\ensuremath{\gamma}$ -排放源可以从我们的方法中合理地获得，尽管存在一些数量上的差异。