通过多步骤介子-重子动力学解决φ介子的定向流难题
Resolving the $ϕ$-meson directed-flow puzzle by multi-step meson--baryon dynamics
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中文总结 AI 辅助
本研究基于PHQMD模型，通过多步骤介子-重子反应解释Au+Au碰撞中φ介子定向流的异常现象，揭示重子主导的产生道及介质效应可解决该难题。
中文摘要 AI 辅助
近期STAR合作组在固定靶束流能量扫描能量下的测量结果显示，Au+Au碰撞中φ介子的定向流大得超乎预期，可与质子和Λ重子的定向流相比，远强于轻奇异介子的定向流。由于φ是含奇异夸克的介子，与非奇异强子的相互作用较弱，这一观测结果被解读为非常规重子动力学或与φ道耦合的奇异重子共振的可能信号。在部分子-强子-量子分子动力学（PHQMD）模型框架内，我们证明在重子密度较高的区域，φ介子主要通过多步骤介子-重子和介子-超子反应产生，这些反应的跃迁振幅由基于扩展SU(6)手征有效拉氏量的耦合道T矩阵计算约束。结合φ谱函数的介质展宽效应，这些重子主导的产生道增强了近阈φ介子的产生，并将富重子源的集体运动印记在产生的φ介子上。
英文摘要
Recent STAR measurements at fixed-target Beam Energy Scan energies have revealed an unexpectedly large directed flow of $ϕ$ mesons in Au+Au collisions, comparable to that of protons and $Λ$ baryons and much stronger than that of light strange mesons. Since the $ϕ$ is a hidden-strangeness meson with relatively weak interactions with non-strange hadrons, this observation has been interpreted as a possible signal of unconventional baryonic dynamics or exotic baryonic resonances coupled to the $ϕ$ channel. Within the framework of the Parton-Hadron-Quantum-Molecular-Dynamics(PHQMD) model, we demonstrate that in the high baryon density region, $ϕ$ mesons are produced predominantly through multi-step meson--baryon and meson--hyperon reactions, whose transition amplitudes are constrained by a coupled-channel $T$-matrix calculation based on an extended SU(6) chiral effective Lagrangian. Together with the in-medium broadening of the $ϕ$ spectral function, these baryon-driven production channels enhance near-threshold $ϕ$ production and imprint the collective motion of the baryon-rich source on the produced $ϕ$ mesons.
