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Relativistic Hadron-Hadron Collisions in the Ultra-Relativistic Quantum Molecular Dynamics Model (UrQMD)

M. Bleicher, E. Zabrodin, C. Spieles, S. A. Bass, C. Ernst, S. Soff, L. Bravina, M. Belkacem, H. Weber, H. Stöcker, W. Greiner

TL;DR

The paper introduces UrQMD as a unified microscopic transport approach for hadron-hadron collisions over a wide energy range, combining resonance/soft processes at low energies with color-string dynamics at high energies. It details the cross-section inputs, including data-driven fits, the Additive Quark Model, and high-energy CERN-HERA parametrizations, and explains resonance and string reaction channels along with finite size corrections. The authors implement color fluctuations and color coherence phenomena, detailing their impact on observables such as multiplicities and rapidity spectra. Comparisons with a broad set of experimental data show generally good agreement, highlighting UrQMD as a practical tool for understanding hadronic interactions in relativistic heavy-ion collisions, while identifying areas where improved hadron-hadron data would enhance predictive power.

Abstract

Hadron-hadron collisions at high energies are investigated in the Ultra-relativistic-Quantum-Molecular-Dynamics approach (UrQMD). This microscopic transport model is designed to study pp, pA and A+A collisions. It describes the phenomenology of hadronic interactions at low and intermediate energies ($\sqrt s <5$ GeV) in terms of interactions between known hadrons and their resonances. At high energies, $\sqrt s >5$ GeV, the excitation of color strings and their subsequent fragmentation into hadrons dominates the multiple production of particles in the UrQMD model. The model shows a fair overall agreement with a large body of experimental h-h data over a wide range of h-h center-of-mass energies. Hadronic reaction data with higher precision would be useful to support the use of the UrQMD model for relativistic heavy ion collisions.

Relativistic Hadron-Hadron Collisions in the Ultra-Relativistic Quantum Molecular Dynamics Model (UrQMD)

TL;DR

The paper introduces UrQMD as a unified microscopic transport approach for hadron-hadron collisions over a wide energy range, combining resonance/soft processes at low energies with color-string dynamics at high energies. It details the cross-section inputs, including data-driven fits, the Additive Quark Model, and high-energy CERN-HERA parametrizations, and explains resonance and string reaction channels along with finite size corrections. The authors implement color fluctuations and color coherence phenomena, detailing their impact on observables such as multiplicities and rapidity spectra. Comparisons with a broad set of experimental data show generally good agreement, highlighting UrQMD as a practical tool for understanding hadronic interactions in relativistic heavy-ion collisions, while identifying areas where improved hadron-hadron data would enhance predictive power.

Abstract

Hadron-hadron collisions at high energies are investigated in the Ultra-relativistic-Quantum-Molecular-Dynamics approach (UrQMD). This microscopic transport model is designed to study pp, pA and A+A collisions. It describes the phenomenology of hadronic interactions at low and intermediate energies ( GeV) in terms of interactions between known hadrons and their resonances. At high energies, GeV, the excitation of color strings and their subsequent fragmentation into hadrons dominates the multiple production of particles in the UrQMD model. The model shows a fair overall agreement with a large body of experimental h-h data over a wide range of h-h center-of-mass energies. Hadronic reaction data with higher precision would be useful to support the use of the UrQMD model for relativistic heavy ion collisions.

Paper Structure

This paper contains 16 sections, 38 equations, 39 figures, 9 tables.

Table of Contents

  1. Motivation
  2. The UrQMD Approach
  3. Cross-Sections
  4. Baryon-Baryon Cross-Sections
  5. Meson-Baryon Cross-Sections
  6. Meson-Meson Cross Sections
  7. Antibaryon$-$Baryon Cross-Sections
  8. The Additive Quark Model (AQM)
  9. Color Fluctuations, Color Opacity and Color Transparency
  10. The Reaction Channels
  11. Resonances
  12. Strings
  13. Finite Size Effects
  14. The Generation of Transverse Momentum
  15. Particle Yields, Longitudinal and Transverse Spectra
  16. ...and 1 more sections

Figures (39)

  • Figure 1: Implemented mesons: pseudo-scalar mesons (left plot) and vector mesons (right plot).
  • Figure 2: Implemented mesons: scalar mesons (left plot) and pseudo-vector mesons (right plot). $f_1$ and $f^\prime_1$ are the states $f_1(1285)$ and $f_1(1420)$, respectively.
  • Figure 3: The total cross-section of $pp$ collisions vs. the laboratory momentum $p_{lab}$ of the incident particle. Data are taken from pdg96.
  • Figure 4: The inelastic cross-section of $pp$ collisions vs. the laboratory momentum $p_{lab}$ and the cross-sections of the various inelastic channels.
  • Figure 5: Cross section for the production of neutral mesons in $pp$. The inclusive and exclusive meson production is compared to data by calen96aflaminio
  • ...and 34 more figures