粲夸克对在质子-原子核碰撞J/ψ 产生过程中的能量损失
Energy Loss of Charm-quark Pair in J/ψ Production From Proton-nucleus Collisions
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摘要: 高能重离子碰撞热核环境中J/ψ产额的压低被认为是夸克胶子等离子体生成的重要信号。研究冷核物质中各种核效应对J/ψ 形成过程的影响，是准确理解热核环境中核效应对J/ψ产额压低机制的重要途径。研究了质子-原子核碰撞J/ψ 产生过程中初态部分子分布函数的核效应、入射质子的能量损失效应、以及末态粲夸克对能量损失效应对J/ψ 粒子产额的压低作用，对质子-原子核碰撞J/ψ产生过程的微分截面比RFe/Be(xF)进行了领头阶的唯象分析，并与E866 实验数据中代表J/ψ粒子在靶核外产生的实验数据进行比较，获取了粲夸克对的能量损失值(3.81±1.71) GeV/fm。研究结果表明，部分子分布函数的核效应对截面比RFe=Be(xF) 的压低作用在xF > 0区域是随着xF 的增大而增大的；末态粲夸克对的能量损失效应是影响J= 粒子产额压低的重要核效应；当xF较大时(0:65≤xF≤0.92)，初态入射质子的能量损失效应在对微分截面比RFe/Be(xF)的压低中起了主要作用。J/ψ suppression observed in hot nuclear matter from heavy-ion collisions is considered as a most reliable signature for the formation of Quark-Gluon Plasma. The study about the nuclear effects on J/ψ production in cold nuclear matter provides an important tool for clarifying the conventional nuclear suppression mechanism in heavy-ion collisions. J/ψ suppression in p-A collisions is studied by considering the nuclear effects on parton distribution, the energy loss of beam proton in initial state, and the finial state energy loss of c¯c pair.The leading-order computations for J/ψ production cross-section ratios RFe=Be(xF) are presented and compared with the selected E866 experimental data with the J/ψ production occurring outside the nucleus, the obtained energy loss of the color octet is (3.81±1.71) GeV/fm. It is found that the nuclear suppression from the nuclear effects on the parton distribution functions becomes larger as the increase of xF in the range xF > 0，the J/ψ suppression on RFe/Be(xF) induced by the energy loss of color octet c¯c is an important nuclear effect, in the region 0:656xF 60:92, the energy loss of beam proton in initial state is the dominant mechanism which causes a reduction of the J/ψ yield.Abstract: J/ψ suppression observed in hot nuclear matter from heavy-ion collisions is considered as a most reliable signature for the formation of Quark-Gluon Plasma. The study about the nuclear effects on J/ψ production in cold nuclear matter provides an important tool for clarifying the conventional nuclear suppression mechanism in heavy-ion collisions. J/ψ suppression in p-A collisions is studied by considering the nuclear effects on parton distribution, the energy loss of beam proton in initial state, and the finial state energy loss of c¯c pair.The leading-order computations for J/ψ production cross-section ratios RFe=Be(xF) are presented and compared with the selected E866 experimental data with the J/ψ production occurring outside the nucleus, the obtained energy loss of the color octet is (3.81±1.71) GeV/fm. It is found that the nuclear suppression from the nuclear effects on the parton distribution functions becomes larger as the increase of xF in the range xF > 0，the J/ψ suppression on RFe/Be(xF) induced by the energy loss of color octet c¯c is an important nuclear effect, in the region 0:656xF 60:92, the energy loss of beam proton in initial state is the dominant mechanism which causes a reduction of the J/ψ yield.
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