Modified string fragmentation function and particle production in nuclear collisions at top RHIC energy

A modified string fragmentation function is assumed in a hadron and string cascade model, LUCIAE (m), accounting for interactions among strings formed at the early stage of relativistic nucleus-nucleus collisions. It turns out that the experimental data of global properties such as the charged multiplicity and the φ meson rapidity density at mid-rapidity in p+p, d+Au and Au+Au collisions at √sNN=200 GeV are reproduced well by LUCIAE (m) rather than by LUCIAE (d) (default LUCIAE). However, LUCIAE (m) fails to account for the suppression of a high pt transverse momentum spectrum observed in central Au+Au collisions at RHIC, even if final state rescatterings among produced hadrons are included in the calculations. This fact indicates that some novel mechanism has to be introduced to understand the suppression of hadron production at high pt