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High-density QCD and cosmic-ray air showers
H J Drescher1, A Dumitru, M Strikman
1Johann Wolfgang Goethe University, Postfach 11 19 32, 60054 Frankfurt, Germany.
Physical Review Letters
|August 11, 2005
Summary
High-energy particle production in Quantum Chromodynamics (QCD) suggests a lighter cosmic ray composition. Data are sensitive to gluon density evolution, indicating slower growth than previously observed.
Area of Science:
- High Energy Physics
- Quantum Chromodynamics (QCD)
- Cosmic Ray Physics
Background:
- The high-energy, small-x limit of QCD predicts large gluon densities in hadrons.
- Understanding particle production in this regime is crucial for interpreting cosmic ray data.
Purpose of the Study:
- To investigate particle production in the high-energy, small-x limit of QCD.
- To analyze the impact of gluon density on cosmic ray air showers.
- To explore sensitivity to different QCD evolution scenarios.
Main Methods:
- Analysis of particle production in the small-x limit of Quantum Chromodynamics.
- Modeling of cosmic-ray induced air showers.
- Comparison with leading-twist models and experimental data.
Main Results:
- Predicted strong modifications to particle phase-space distributions.
- Suggests a light composition for hadronic primaries near the Greisen-Zatsepin-Kuzmin cutoff.
- Cosmic ray data are sensitive to fixed-coupling and running-coupling Balitsky-Fadin-Kuraev-Lipatov evolution scenarios.
Conclusions:
- The gluon density growth appears slower than at RHIC and HERA, possibly due to running-coupling effects.
- Cosmic ray observations provide insights into the behavior of QCD at high energies.
- Results imply a lighter cosmic ray composition at extreme energies.
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