N/Z Dependence of Projectile Fragmentation

TL;DR

This study investigates how the neutron-to-proton ratio (N/Z) influences projectile fragmentation at relativistic energies, using advanced detection methods to analyze isotope yields and explore nuclear properties at freeze-out.

Contribution

It provides new experimental data on N/Z dependence in projectile fragmentation using diverse isotopic beams and high-resolution detection, challenging existing theoretical predictions.

Findings

Isoscaling observed in isotope yields.

Chemical freeze-out temperatures are isotopically independent.

Results contradict finite-temperature Hartree-Fock predictions.

Abstract

The N/Z dependence of projectile fragmentation at relativistic energies has been studied in a recent experiment at the GSI laboratory with the ALADiN forward spectrometer coupled to the LAND neutron detector. Besides a primary beam of 124Sn, also secondary beams of 124La and 107Sn delivered by the FRS fragment separator have been used in order to extend the range of isotopic compositions of the produced spectator sources. With the achieved mass resolution of \Delta A/A \approx 1.5%, lighter isotopes with atomic numbers Z \le 10 are individually resolved. The presently ongoing analyses of the measured isotope yields focus on isoscaling and its relation to the properties of hot fragments at freeze-out and on the derivation of chemical freeze-out temperatures which are found to be independent of the isotopic composition of the studied systems. The latter result is at variance with the predictions for limiting temperatures as obtained with finite-temperature Hartree-Fock calculations.