## Abstract

This is a concise introduction to the topic of nonextensive Tsallis statistics meant especially for those interested in its relation to high-energy proton-proton, proton-nucleus and nucleus-nucleus collisions. The three types of Tsallis statistics are reviewed. Only one of them is consistent with the fundamental hypothesis of equilibrium statistical mechanics. The single-particle distributions associated with it, namely Boltzmann, Fermi-Dirac and Bose-Einstein, are derived. These are not equilibrium solutions to the conventional Boltzmann transport equation which must be modified in a rather nonintuitive manner for them to be so. Nevertheless, the Boltzmann limit of the Tsallis distribution is extremely efficient in representing a wide variety of single-particle distributions in high-energy proton-proton, proton-nucleus and nucleus-nucleus collisions with only three parameters, one of them being the so-called nonextensitivity parameter q. This distribution interpolates between an exponential at low transverse energy, reflecting thermal equilibrium, to a power law at high transverse energy, reflecting the asymptotic freedom of Quantum Chromodynamics (QCD). It should not be viewed as a fundamental new parameter representing nonextensive behavior in these collisions.

Original language | English (US) |
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Article number | 2130006 |

Journal | International Journal of Modern Physics E |

Volume | 30 |

Issue number | 8 |

DOIs | |

State | Published - Aug 1 2021 |

### Bibliographical note

Funding Information:This work was supported by the U.S. Department of Energy Grant DE-FG02-87ER40328.

Publisher Copyright:

© 2021 World Scientific Publishing Company.

## Keywords

- Statistical mechanics
- Tsallis distributions
- high energy nuclear and particle collisions