[Paper Review] Analysis of Intermediate-Energy Nucleus-Nucleus Spallation, Fission, and Fragmentation Reactions with the LAQGSM code

S. G. Mashnik, K. K. Gudima+2 more|ArXiv.org|Aug 14, 2003

Nuclear reactor physics and engineering3 citations

TL;DR

This paper presents the LAQGSM code, a Monte Carlo event generator for intermediate-energy nucleus-nucleus reactions, which combines the Intranuclear Cascade and Modified Exciton Model for preequilibrium decay with the Quark-Gluon String Model for high-energy interactions. It successfully reproduces neutron spectra and fragment yields from 95–600 MeV/nucleon reactions on carbon to lead targets, and cross sections for spallation, fission, and fragmentation up to 1 GeV/nucleon, demonstrating strong agreement with experimental data without parameter fitting.

ABSTRACT

The LAQGSM code has been recently developed at Los Alamos National Laboratory to simulate nuclear reactions for proton radiography applications. We have benchmarked our code against most available measured data both for proton-nucleus and nucleus-nucleus interactions at incident energies from 10 MeV to 800 GeV and have compared our results with predictions of other current models used by the nuclear community. Here, we present a brief description of our code and show illustrative results obtained with LAQGSM for neutron spectra measured recently by Nakamura's groups for reactions induced by light and medium nuclei on targets from C to Pb at several incident energies from 95 to 600 MeV/nucleon and with the recent GSI measurements of spallation, fission, and fragmentation yields from A+p and A+A reactions at incident energies near and below 1 GeV/nucleon. Further necessary work is outlined.

Motivation & Objective

• To develop and validate the LAQGSM code for simulating intermediate-energy nucleus-nucleus reactions across a broad energy range.
• To benchmark LAQGSM against experimental data for neutron spectra and fragment yields from light and medium nuclei on targets from 12C to 208Pb.
• To assess the predictive power of LAQGSM in comparison with other models, particularly for spallation, fission, and fragmentation reactions.
• To identify limitations in current implementations, especially regarding angular momentum and electromagnetic fission, and to guide future code improvements.

Proposed method

• LAQGSM uses modules from CEM2k to model the preequilibrium and evaporation stages of nuclear reactions.
• It incorporates the Quark-Gluon String Model (QGSM) for high-energy interactions up to 1 TeV/nucleon, including cascade dynamics and final-state coalescence of light ions.
• The code enforces exact momentum-energy conservation per event and uses realistic binding energies and reduced masses in emission calculations.
• Fragmentation and fission yields are further refined by merging LAQGSM with the GEM2 evaporation model and tested against GSI and Nakamura group data.
• The model includes improved treatment of level-density parameters, fission barriers, and Pauli blocking during cascade and preequilibrium stages.
• Monte Carlo simulations are used to generate event-by-event reaction outcomes, with statistical sampling adjusted for low-yield, neutron-rich nuclides.

Experimental results

Research questions

• RQ1 How accurately does LAQGSM reproduce measured neutron spectra from 95–600 MeV/nucleon nucleus-nucleus reactions on targets from 12C to 208Pb?
• RQ2 Can LAQGSM+GEM2 describe the full range of fragment yields, including fission and spallation products, across multiple incident energies and target-projectile combinations?
• RQ3 Why does LAQGSM+GEM2 fail to reproduce mass distributions in 1 GeV/nucleon 238U + 208Pb fission, and what physical factors contribute to this discrepancy?
• RQ4 To what extent do limitations in current LAQGSM and GEM2, such as lack of angular momentum and electromagnetic fission, affect predictions for heavy-ion systems?
• RQ5 How do the results of LAQGSM+GEM2 compare with those from the abrasion-ablation model and QMD simulations for projectile fragmentation?

Key findings

• LAQGSM+GEM2 reproduces measured neutron spectra from 12C to 208Pb targets across 95–600 MeV/nucleon with good agreement, especially for light and medium nuclei.
• The code successfully describes fragment yields from 17–21O beams on 12C targets, matching experimental cross sections for Zf and Af distributions, with predictions for unmeasured isotopes.
• For 238U + 64Cu at 950 MeV/nucleon, LAQGSM+GEM2 reproduces all measured product cross sections across six orders of magnitude, with minor overestimation for very neutron-rich nuclides likely due to low statistics.
• The model shows strong agreement with 208Pb + 64Cu at 1 GeV/nucleon, accurately predicting cross sections for a wide range of fragments.
• For 40Ar on 9Be at 1.05 GeV/nucleon, LAQGSM+GEM2 matches experimental cross sections for B to F isotopes, including predictions for unmeasured isotopes.
• Discrepancies in mass distributions for 1 GeV/nucleon 238U + 208Pb fission are attributed to missing electromagnetic fission and lack of angular momentum treatment in the current code version.