Bimodality in spectator fragmentation

TL;DR

This paper investigates bimodal distributions in spectator fragmentation of gold collisions, revealing finite-size effects and configurational fluctuations that are characteristic of small-system fragmentation processes.

Contribution

It demonstrates that bimodality in fragment charge distributions is a finite-size effect related to percolation phenomena in small nuclear systems.

Findings

Bimodal distributions observed at specific Z_bound values.

Bimodality linked to finite-size effects similar to percolation.

Configurational fluctuations are generic in small-system fragmentation.

Abstract

The fluctuations of the largest fragment charge of a partition and of the charge asymmetries of the two or three largest fragments in spectator decays following 197Au + 197Au collisions at 1000 MeV per nucleon are investigated. The observed bimodal distributions at specific values of the sorting variable Z_bound exhibit features known from percolation theory where they appear as finite-size effects. The underlying configurational fluctuations seem generic for fragmentation processes in small systems.