New measurement of the elemental fragmentation cross sections of 218 MeV/nucleon 28 Si on a carbon target

TL;DR

This study presents a new measurement of elemental fragmentation cross sections for 28Si on carbon at 218 MeV/nucleon, comparing results with models and revealing insights into the reaction mechanisms and odd-even staggering effects.

Contribution

It provides the first EFCS measurement at this energy for 28Si on carbon and evaluates model performances, highlighting the importance of the statistical decay stage in fragmentation.

Findings

IQMD+GEMINI model accurately reproduces EFCSs within 3.5% for ΔZ ≤ 5.

Most models fail to capture the odd-even staggering in elemental distributions.

Odd-even staggering occurs during the sequential statistical decay stage, not the initial collision.

Abstract

Elemental fragmentation cross sections (EFCSs) of stable and unstable nuclides have been investigated with various projectile-target combinations at a wide range of incident energies. These data are critical to constrain and develop the theoretical reaction models and to study the propagation of galactic cosmic rays (GCR). In this work, we present a new EFCS measurement for $^{28}$Si on carbon at 218~MeV/nucleon performed at the Heavy Ion Research Facility (HIRFL-CSR) complex in Lanzhou. The impact of the target thickness has been well corrected to derive an accurate EFCS. Our present results with charge changes $\Delta Z$ = 1-6 are compared to the previous measurements and to the predictions from the models modified EPAX2, EPAX3, FRACS, ABRABLA07, NUCFRG2, and IQMD coupled with GEMINI (IQMD+GEMINI). All the models fail to describe the odd-even staggering strength in the elemental distribution, with the exception of the IQMD+GEMINI model, which can reproduce the EFCSs with an accuracy of better than 3.5\% for $\Delta Z\leq5$. The IQMD+GEMINI analysis shows that the odd-even staggering in EFCSs occurs in the sequential statistical decay stage rather than in the initial dynamical collision stage. This offers a reasonable approach to understand the underlying mechanism of fragmentation reactions.