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arXiv 1801.07557hep-phnucl-th
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相对论性重离子碰撞中的重子-反重子动力学

Baryon-antibaryon dynamics in relativistic heavy-ion collisions

Eduard Seifert, Wolfgang Cassing

摘要:

在夸克重排模型(QRM)的基础上,采用粒子-强子-弦动力学(PHSD)输运方法,研究了Pb+Pb和Au+Au碰撞中重子-反重子湮灭和再生($B{\bar B} \leftrightarrow 3 M$)动力学随中心度的变化.在相对论重离子对撞机(RHIC)的能量,我们发现一个小的净减少重子-反重子($B {\bar B}$)对,而对于大型强子对撞机的能量$\sqrt{s_{NN}}$ = 2.76 GeV的一个小的净增强被发现相对于没有湮灭(和再生)通道的计算。因此,在$\sqrt{s_{NN}}$ = 2.76 TeV的Pb+Pb碰撞中,质子和反质子产额\cite{53}的数据和统计计算之间的相当大的差异,不应该归因于净反质子湮灭,其中2.7 $σ$的偏差被爱丽丝合作组织声称。这与观测结果一致,即对于反超子,数据和统计强子化模型(SHM)计算之间没有实质性偏差,因为根据PHSD分析,反超子应该被修改与反质子相同的量。由于粒子比率的PHSD结果与ALICE数据一致(在误差线内),这可能指向强子化(至少对于质子/反质子)中的统计平衡的偏离。此外,我们发现,$B {\bar B} \leftrightarrow 3 M$反应是更有效的,在较低的SPS能量的反质子和反超子的净抑制高达2 - 2.5的因素,可以提取从PHSD计算中心Au+Au碰撞。

英文摘要:

The dynamics of baryon-antibaryon annihilation and reproduction ($B{\bar B} \leftrightarrow 3 M$) is studied within the Parton-Hadron-String Dynamics (PHSD) transport approach for Pb+Pb and Au+Au collisions as a function of centrality from lower Super Proton Synchrotron (SPS) up to Large Hadron Collider (LHC) energies on the basis of the quark rearrangement model (QRM). At Relativistic Heavy-Ion Collider (RHIC) energies we find a small net reduction of baryon-antibaryon ($B {\bar B}$) pairs while for the LHC energy of $\sqrt{s_{NN}}$ = 2.76 GeV a small net enhancement is found relative to calculations without annihilation (and reproduction) channels. Accordingly, the sizeable difference between data and statistical calculations in Pb+Pb collisions at $\sqrt{s_{NN}}$= 2.76 TeV for proton and antiproton yields \cite{53}, where a deviation of 2.7 $σ$ was claimed by the ALICE Collaboration, should not be attributed to a net antiproton annihilation. This is in line with the observation that no substantial deviation between the data and statistical hadronization model (SHM) calculations is seen for antihyperons, since according to the PHSD analysis the antihyperons should be modified by the same amount as antiprotons. As the PHSD results for particle ratios are in line with the ALICE data (within error bars) this might point towards a deviation from statistical equilibrium in the hadronization (at least for protons/antiprotons). Furthermore, we find that the $B {\bar B} \leftrightarrow 3 M$ reactions are more effective at lower SPS energies where a net suppression for antiprotons and antihyperons up to a factor of 2 -- 2.5 can be extracted from the PHSD calculations for central Au+Au collisions.

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