Collective expansion in central Au+Au collisions.
نویسندگان
چکیده
Energy spectra for intermediate mass fragments produced in central Au + Au collisions at E/A = 100 MeV indicate a collective expansion at breakup. For the first time, values for this collective expansion energy per nucleon are extracted independently for each charge. Typically, these values are one-third to one-half of the incident kinetic energy per nucleon in the c.m. system, but they decrease with Zf, suggesting that all fragments do not participate equally in the collective expansion. Investigations of central nucleus-nucleus collisions reveal that the multiplicity of intermediate mass fragments (IMF's: ZI = 3 — 30) increases with incident energy to a maximum at Eb, /A = 100 MeV and declines thereafter [1,2]. Such observations are qualitatively consistent with the excitation energy dependences of statistical models [3 — 5] and nuclear phase transitionsdict the fragment multiplicities to be strongly influenced by a rapid expansion from supranormal densities achieved early in the nuclear collision [8], and experimental evidence now suggests a significant collective "radial" expansion [10 — 13]. This collective expansion may persist to lower incident energies where sidewards directed flow [14 — 16] vanishes [17,18] due to cancellations between the attractive and repulsive deflections that result from mean field attraction and nucleon-nucleon collisions, respectively. Like measurements of directed transverse flow [14 — 16], measurements of radial flow [10,13] can provide unique constraints on nuclear transport properties such as the nuclear equation of state [19].
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ورودعنوان ژورنال:
- Physical review letters
دوره 73 25 شماره
صفحات -
تاریخ انتشار 1994