While the main features of atomic nuclei are well described by nuclear mean-field models, there is a large and growing body of evidence which indicates an important additional role played by spatially-correlated nucleon–nucleon structures. The role of nucleonic structures was first suggested by Heidmann in 1950 to explain the pick-up reactions of energetic nucleons. Since then, a steady flux of new experimental evidence has confirmed the presence of similar structures inside atomic nuclei, dominated by correlations between pairs of nucleons. The role of these internal nucleon–nucleon correlations has been established using various energetic probes like photons, pions, leptons and hadrons. These correlated structures are essential for understanding the interaction of particles with nuclei and their presence provides an explanation of many specific nuclear phenomena, including backscattered protons, copious deuteron production, sub-threshold particle production, neutrino interactions with nuclei and the European Muon Collaboration effect. On the theoretical side, these measurements have stimulated a large number of phenomenological models specifically devised to address these enigmatic observations. While reviews exist for specific interactions, there is currently no published commentary which systematically encompasses the wide range of experimental signatures and theoretical frameworks developed thus far. The present review draws together the synergies between a wide range of different experimental and theoretical studies, summarizes progress in this area and highlights outstanding issues for further study.

中文翻译：

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原子核内的核子-核子相关性：协同作用、观察和理论模型

虽然核平均场模型很好地描述了原子核的主要特征，但有大量且不断增长的证据表明，空间相关的核子-核子结构发挥着重要的附加作用。海德曼于 1950 年首次提出核子结构的作用，以解释高能核子的拾取反应。从那时起，不断涌现的新实验证据证实了原子核内部存在类似的结构，主要是核子对之间的相关性。这些内部核子-核子相关性的作用已经通过光子、π介子、轻子和强子等各种高能探针建立起来。这些相关结构对于理解粒子与原子核的相互作用至关重要，它们的存在为许多特定的核现象提供了解释，包括背散射质子、大量氘核的产生、亚阈值粒子的产生、中微子与原子核的相互作用以及欧洲介子协作效应。在理论方面，这些测量激发了大量专门为解决这些神秘观察而设计的现象学模型。虽然存在针对特定相互作用的评论，但目前还没有发表的评论系统地涵盖迄今为止开发的广泛的实验特征和理论框架。本综述汇集了各种不同实验和理论研究之间的协同作用，总结了该领域的进展，并强调了需要进一步研究的突出问题。