New experimental evidence for universal odd-even staggering in fragmentation cross sections

Abstract

About 100 isotopes with $(N\ensuremath{-}Z)$ from 1--9 produced by 300 MeV/nucleon $^{78}\mathrm{Kr}$ projectiles impinging on an ${\mathrm{Al}}_{2}{\mathrm{O}}_{3}$ target have been separated and identified at the RIBLL2 separator of HIRFL, where their production yields have been measured. The odd-even staggering (OES) in these experimental yields is quantitatively studied by employing a third-order difference formula. Measured data are used to validate the universality of this OES by comparing with other experimental data produced by fragmentation of different krypton projectiles on various targets as well as the OES evaluated from thousands of accurate cross sections measured in many different reactions. These comparisons between experimental data from a large variety of fragmentation reactions provide strong evidence that the OES magnitude almost does not depend on the projectile-target combinations and thus the OES is universal for different reaction systems. The OES magnitudes in these experimental data are also applied to examine the OES predicted by the abrasion-ablation model. There are large discrepancies between the OES magnitudes in predicted and measured cross sections.