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arXiv · 2312.10161

Transverse momentum fluctuation in ultra-central Pb+Pb collision at the LHC

Rupam Samanta·Somadutta Bhatta·Jiangyon Jia·Matthew Luzum·Jean-Yves Ollitrault
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Abstract

The ATLAS collaboration has recently observed that the variance of the transverse momentum per particle ($[ p_t ]$), when measured as a function of the collision multiplicity ($N_{ch}$) in Pb+Pb collisions, decreases by a factor $2$ for the largest values of $N_{ch}$, corresponding to ultra-central collisions. We show that this phenomenon is naturally explained by invoking impact parameter ($b$) fluctuations, which contribute to the variance, and gradually disappear in ultra-central collisions. It implies that $N_{ch}$ and $[ p_t ]$ are strongly correlated at fixed $b$, which is explained by the local thermalization of the QGP medium.

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Rupam Samanta, Somadutta Bhatta, Jiangyon Jia, Matthew Luzum, Jean-Yves Ollitrault. 2023-12-15. Transverse momentum fluctuation in ultra-central Pb+Pb collision at the LHC. https://arxiv.org/abs/2312.10161

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