Fragmentation of Nuclear Remnants in Electron-Nucleus Collisions at High Energy as a Nonextensive Process

It is widely accepted that the various internal structures of an excited nucleus can lead to different topological configurations of nuclear fragments during fragmentation. However, these internal structures may transition from one configuration to another with varying probabilities. Utilizing a partitioning method based on equal (or unequal) probabilities – without incorporating the alpha-cluster ($α$-cluster) model – allows for the derivation of diverse topological configurations of nuclear fragments resulting from fragmentation. Subsequently, we predict the multiplicity distribution of nuclear fragments for specific excited nuclei, such as $^9$Be$^$, $^{12}$C$^$, and $^{16}$O$^*$, which can be formed as nuclear remnants in electron-nucleus ($eA$) collisions at high energy. According to the $α$-cluster model, an $α$-cluster structure should take precedence among different internal structures; this may result in deviations in the multiplicity distributions of nuclear fragments with charge $Z=2$, compared to those predicted by the partitioning methods. Furthermore, in the framework of Tsallis statistics, the nonextensive generalized temperature, entropy index, and $q$-entropy are obtained from the multiplicity distribution of nuclear fragments with given charge number. Our work shows that fragmentation of nuclear remnants in electron-nucleus collisions at high energy is a nonextensive process.

💡 Research Summary

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The manuscript investigates the fragmentation of excited nuclear remnants produced in high‑energy electron‑nucleus (eA) collisions, focusing on three representative nuclei: ⁹Be*, ¹²C* and ¹⁶O*. The authors adopt a purely statistical “partitioning” approach to generate all possible charge‑conserving fragment configurations without invoking any specific nuclear‑structure model such as the α‑cluster picture. Two distinct partitioning schemes are considered:

1. Equal‑probability partitioning – every admissible set {N_Z(Z)} of fragment charges is assigned the same weight. The number of distinct partitions is given by the multinomial coefficient M₁ = Q! / ∏_Z N_Z(Z)!, where Q is the total charge of the excited nucleus. Consequently the probability of any configuration is f₁ = 1/Ω, Ω being the total number of partitions.

2. Unequal‑probability partitioning – the weight of a configuration is proportional to the number of distinct permutations, M₂ = Q! /