AI 中文总结
研究重离子在SPS能量下碰撞时，用强子输运模型UrQMD探讨重子-反重子湮灭对超子产生及$\bar{\Lambda}$/$\bar{p}$比率的影响，发现$\bar{\Lambda}$/$\bar{p}$增强未必因奇异增强，重子-反重子湮灭起重要作用。
AI 中文摘要
相对论能量下重核碰撞会产生夸克-胶子等离子体（QGP），其形成常伴有奇异增强现象，即中心碰撞中奇异粒子与非奇异粒子的相对产生比周边或质子-质子相互作用时增强。除了K/$\pi$比率增强外，CERN SPS处$\bar{\Lambda}$与$\bar{p}$比率还存在非单调能量依赖性，也归因于奇异增强。反粒子直接由反应产生，$\bar{\Lambda}$/$\bar{p}$比率被视为奇异增强的更纯净探针。但在此能量范围强子相互作用起主导作用，重子-反重子（$\mathrm{B\bar{B}}$）湮灭等过程对$\bar{\Lambda}$和$\bar{p}$有重大影响。本工作用强子输运模型UrQMD研究$\mathrm{B\bar{B}}$湮灭对$Λ$、$\barΛ$超子产生的作用及其对$\bar{\Lambda}$/$\bar{p}$比率的影响。含$\mathrm{B\bar{B}}$湮灭的UrQMD计算能得出$Λ$和$\barΛ$平均横向质谱趋势以及$\bar{\Lambda}$/$\bar{p}$比率随中心度和碰撞能量的特征增强。此外，经馈降校正的SPS数据提取的$\bar{\Lambda}$/$\bar{p}$比率与含$\mathrm{B\bar{B}}$湮灭的UrQMD模型计算结果吻合良好。这表明$\bar{\Lambda}$/$\bar{p}$增强不一定源于奇异增强，$\mathrm{B\bar{B}}$湮灭起重要作用。
英文摘要
A deconfined medium of quarks and gluon, called the Quark-Gluon Plasma (QGP) is produced when heavy-nuclei are collided at relativistic energies. The QGP formation is often characterized by a phenomenon called strangeness enhancement where, the relative production of strange-to-non-strange particles are enhanced in central collisions compared to peripheral or proton-proton interactions. Besides the enhancement in K/$π$ ratios, a non-monotonic energy dependence was also reported for $\barΛ$ to $\bar{p}$ ratios at CERN SPS, attributed to a signature for the strangeness enhancement as well. As anti-particles are produced directly from the reaction, the $\barΛ$/$\bar{p}$ ratios are considered as a cleaner probe for the strangeness enhancement. However, at this energy range hadronic interactions have a dominant role to play and, importantly for $\barΛ$ and $\bar{p}$, processes like baryon-anti-baryon ($\mathrm{B\bar{B}}$) annihilation can have a significant impact. In this work, we use a hadronic transport model UrQMD, to investigate the role of baryon-anti-baryon ($\mathrm{B\bar{B}}$) annihilation on $Λ$, $\barΛ$ hyperon production and its effect on $\barΛ$/$\bar{p}$ ratios. The UrQMD calculations that include $\mathrm{B\bar{B}}$ annihilation can produce the trend of average transverse mass spectra for $Λ$ and $\barΛ$, as well as, the characteristic enhancement in $\barΛ$/$\bar{p}$ ratios in data as a function of centrality and collision energy. Furthermore, $\barΛ$/$\bar{p}$ ratios extracted from the feed-down corrected SPS data are seen to be in good agreement with UrQMD model calculations with $\mathrm{B\bar{B}}$ annihilation. This suggests that $\barΛ$/$\bar{p}$ enhancement is not necessarily because of strangeness enhancement and $\mathrm{B\bar{B}}$ annihilation has a significant role to play.
Journal refEur.Phys.J.A 58 (2022) 10, 199
DOI：10.1140/epja/s10050-022-00856-x
