【摘要】 用相对论输运模型模拟了束流动能为520MeV/u的²³⁸U²³⁸U碰撞实验．研究了在两种极端对撞方位的UU碰撞中,末态核子和π介子椭圆流v₂与碰撞参数、快度以及横动量的依赖关系．研究表明,由于挤压（squeeze-out）效应,末态核子和π具有负的椭圆流;体-体UU中心碰撞事件具有最大初始坐标空间形变,因而具有最大的负的椭圆流,约12%;在最小无偏事件样本下,体-体和头-头碰撞,中央快度平台上的核子椭圆流大小相当,而前者π椭圆流略大于后者;在中央快度平台,低横动量核子和π主要由反应后期Δ衰变得到,而高横动量主要是参与核子再散射生成,因而在低横动量区它们具有相似的流,而在较高横动量区（＞0．3GeV/c）由于旁观核子的再散射和吸收效应,它们的椭圆流有明显压低．更多还原

【Abstract】 We employ here a Relativistic Transport （ART） Model for Uranium+Uranium collisions at E_b=0.52GeV/u. We study the impact parameter,rapidity and transverse momentum dependence of elliptic flow v₂ for nucleons and pions in two extreme orientation UU collisions.It indicates that elliptic flow of nucleons and pions are always out-of plane as a result of squeeze-out effect.The maximal absolute value of elliptic flow,which is about 12%,appears in body- body certral UU collisons when the initial spatial anisotropy reach the maximum.In minibias events,the magnitudes of elliptic flow are similar for mid-rapidity nucleons in tip-tip and body-body UU collisions,but which is smaller for mid-rapidity pions in tip-tip.Nucleons and pions are produced primarily byΔdecay at low transverse momentum and by participator rescattering at high transverse momentum.Thus,elliptic flow in tip-tip and body-body are similar and have a visible drop in higher transverse momentum （P_t＞0.3GeV/c） as a result of spectators rescatterings and reabsorbtionas.更多还原