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arXiv 2006.12951nucl-thhep-ph
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理解重离子碰撞中$B_2$的能量依赖性：体积和空间-动量关联的相互作用

Understanding the energy dependence of $B_2$ in heavy ion collisions: Interplay of volume and space-momentum correlations

Vincent Gaebel, Michel Bonne, Tom Reichert, Ajdin Burnic, Paula Hillmann, Marcus Bleicher

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6 pages, 6 figures
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摘要：

利用超相对论量子分子动力学（UrQMD）输运模型，并辅以逐事件相空间聚结模型，分析了质子+质子和核+核碰撞中的氘聚结参数$B_2$，能量范围分别为：质子+质子的聚结参数$\sqrt{s_{NN}}=$ 900 - 7000 GeV和核+核碰撞的聚结参数$\sqrt{s_{NN}}=$ 2 - 2760 GeV.将计算结果与E866、E877、PHENIX、STAR和ALICE实验的数据进行了比较。$B_2$值由质子和氘核的最终光谱计算。在较低的能量下，$\sqrt{s_{NN}}\leq 20$ GeV，$B_2$随能量增加而急剧下降。计算结果证实，这是由于$B_2\sim 1/V$中反映的冻结体积增加所致。在较高能量下，$\sqrt{s_{NN}}\geq 20$ GeV、$B_2$以恒定水平饱和。这种质的变化和消失的体积抑制被证明是由于强大的径向流的发展，随着能量的增加。流动导致强烈的空间动量相关性，抵消了体积效应。

英文摘要：

The deuteron coalescence parameter $B_2$ in proton+proton and nucleus+nucleus collisions in the energy range of $\sqrt{s_{NN}}=$ 900 - 7000 GeV for proton+proton and $\sqrt{s_{NN}}=$ 2 - 2760 GeV for nucleus+nucleus collisions is analyzed with the Ultrarelativistic Quantum Molecular Dynamics (UrQMD) transport model, supplemented by an event-by-event phase space coalescence model for deuteron and anti-deuteron production. The results are compared to data by the E866, E877, PHENIX, STAR and ALICE experiments. The $B_2$ values are calculated from the final spectra of protons and deuterons. At lower energies, $\sqrt{s_{NN}}\leq 20$ GeV, $B_2$ drops drastically with increasing energy. The calculations confirm that this is due to the increasing freeze-out volume reflected in $B_2\sim 1/V$. At higher energies, $\sqrt{s_{NN}}\geq 20$ GeV, $B_2$ saturates at a constant level. This qualitative change and the vanishing of the volume suppression is shown to be due to the development of strong radial flow with increasing energy. The flow leads to strong space-momentum correlations which counteract the volume effect.

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