Heavy ion collisions present exciting opportunities to study the effects of quantum coherence in the formation of subatomic particle showers. We report on the first calculation of the momentum sharing and angular separation distributions between the leading subjets inside a reconstructed jet in such collisions. These observables are directly sensitive to the hardest branching within jets and can probe the early stage of the jet formation. We find that the leading-order medium-induced splitting functions, here obtained in the framework of soft-collinear effective theory with Glauber gluon interactions, capture the essential many-body physics, which is different from proton-proton reactions. Qualitative and in most cases quantitative agreement between theory and preliminary CMS measurements suggests that hard parton branching in strongly interacting matter can be dramatically modified. We also propose a new measurement that will illuminate its angular structure.

中文翻译：

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在重离子碰撞中探测射流中最困难的分支

重离子碰撞为研究量子相干性在亚原子粒子簇射形成中的研究提供了令人兴奋的机会。我们报告了在这种碰撞中重建喷气机内部的主导子喷气机之间的动量共享和角间隔分布的首次计算。这些观测资料直接对射流中最硬的分支敏感，可以探测射流形成的早期阶段。我们发现，在软共线有效理论框架下与格劳伯胶子相互作用的前导介质诱导分裂函数，捕获了本质上与质子-质子反应不同的多体物理学。理论与CMS初步测量之间的定性和大多数情况下的定量一致性表明，强烈相互作用的物质中的硬质parton分支可以显着改变。我们还提出了一种新的测量方法，可以阐明其角度结构。