High-Density QCD and Cosmic-Ray Air Showers

H. J. Drescher, A. Dumitru, M. Strikman

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23 Scopus citations


We discuss particle production in the high-energy, small-x limit of QCD where the gluon density of hadrons is expected to become nonperturbatively large. Strong modifications of the phase-space distribution of produced particles as compared to leading-twist models are predicted, which reflect in the properties of cosmic-ray induced air showers in the atmosphere. Assuming hadronic primaries, our results suggest a light composition near Greisen-Zatsepin-Kuzmin cutoff energies. We also show that cosmic-ray data are sensitive to various QCD evolution scenarios for the rate of increase of the gluon density at small x, such as fixed-coupling and running-coupling Balitsky-Fadin-Kuraev-Lipatov evolution. There are clear indications for a slower growth of the gluon density as compared to RHIC and HERA, due, e.g., to running-coupling effects.

Original languageEnglish (US)
Article number231801
JournalPhysical review letters
Issue number23
StatePublished - Jun 17 2005

All Science Journal Classification (ASJC) codes

  • General Physics and Astronomy


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