200GeV/u的^(238)U+^(238)U核碰撞产生的双轻子谱(M≤4GeV/c^2)的计算

Calculation of the Productive Dilepton Spectrum (M≤4GeV/c^2) in ^(238)U+^(238)U Collisions at E_(c,m) ≈200GeV/u

在夸克味动力学的计算中，除包含ｕ、ｄ、ｓ夸克及其反夸克外，还涉及粲夸克及其反夸克（ｃｃ），采用包含夸克味动力学效应的相对论性流体力学模型，计算了碰撞能量为２００ＧｅＶ／ｕ的２３８Ｕ＋２３８Ｕ核碰撞时形成的膨胀ＱＧＰ及其在相变过程中发射的双轻子谱，轻子对的质量范围Ｍ≤４ＧｅＶ／ｃ２．计算结果与ＣＥＲＮＳＰＳ的实验测量数据进行了定性的比较和分析，得到初步的结论：由于夸克碎块和味动力学效应，Ｊ／ψ→μ＋＋μ－峰值被降低，导致低质量区（阈至１．３５ＧｅＶ／ｃ２）谱的提高．

In this paper, besides including u, d, s quarks and their anti-quarks thecharm quarks and their anti-quarks (cc) were still included in the calculation offlavour kinetics of quarks. Using relativitic hydrodynamics model with the effect ofquark flavor kinetics, invariable mass dilepton spectrum of M≤4GeV/c2 has beencalculated. The dileptons are eastted from Phase transihon process of an expansionquark matter which is created in collisions of 238U+238U at energy～200GeV/u. Thenumerical results have been compared with experimental dare of CERN SPSqualitatively. A prelimings conclusion has been given: quark fragmentation and effectof flavour kinetics are the causes of suppression of the peak of J/ψ→μ+μ-.