We discuss the scaling laws of both the charged fragments multiplicity $n$ fluctuations and the charge of the largest fragment $Z_{\max }$ fluctuations for $\mathrm{Xe}+\mathrm{Sn}$ collisions in the range of bombarding energies between $25A\mathrm{MeV}$ and $50A\mathrm{MeV}$. We show at $E_{\mathrm{lab}}\gtrsim 32\mathrm{MeV}/A$ the transition in the fluctuation regime of $Z_{\max }$ which is compatible with the transition from the ordered to disordered phase of excited nuclear matter. The size (charge) of the largest fragment is closely related to the order parameter characterizing this process.

• Received 10 October 2000

DOI:https://doi.org/10.1103/PhysRevLett.86.3514