Limiting fragmentation and $\phi$ meson production at RHIC
The PHOBOS's limiting fragmentation etc. three empirical scaling rules for charged multiplicity in $Au+Au$ collisions at RHIC are investigated by a hadron and string cascade model LUCIAE. Similar studies are performed for the $\phi$ meson exploring its production mechanism via comparing with the charged multiplicity. The LUCIAE results for charged multiplicity are compatible with PHOBOS observations. However, for the $\phi$ meson the three empirical scaling rules are either kept only or kept better in the LUCIAE calculations without reduction mechanism of the $s$ quark suppression extra introduced for the strangeness in LUCIAE model. These results seem indicating a universal production mechanism for charged particle and $\phi$ meson in string fragmentation regime. It is discussed that the PHOBOS's empirical scaling rules are model dependent indeed.