Publication : t19/056

pT-Dependent Particle Number Fluctuations From Principal Component Analyses in Hydrodynamic Simulations of Heavy-Ion Collisions

Gardim Fernando G. (CEA, IPhT (Institut de Physique Théorique), F-91191 Gif-sur-Yvette, France)
Grassi F. (Instituto de Física, Universidade São Paulo, CEP 05508-090 Cidade Universitaria, São Paulo - Brasil)
Ishida P. (Instituto de Física, Universidade São Paulo, CEP 05508-090 Cidade Universitaria, São Paulo - Brasil)
Luzum M. (Departamento de Física Matemática Instituto de Física Universidade de São Paulo C.P. 66318 05315-970, São Paulo, Brazil)
Ollitrault J.-Y. (CEA, IPhT (Institut de Physique Théorique), F-91191 Gif-sur-Yvette, France)
Abstract:
We carry out a principal component analysis of fluctuations in a hydrodynamic simulation of heavy-ion collisions, and compare with experimental data from the CMS collaboration. The leading and subleading principal components of elliptic and triangular flow reproduce the trends seen in data. By contrast, the principal components of multiplicity fluctuations show an interesting difference in their pT dependence for simulations compared to experimental data. Specifically, the leading component increases with pT in hydrodynamics, while it is constant in experiment. In order to understand how the leading and subleading modes arise, we construct a toy model where the principal components have a simple analytic form. We show how the PCA components depend on fluctuations of the average transverse momentum and of the total multiplicity, as well as correlations between the two, and we verify that hydrodynamic simulations agree with the predictions of the toy model. The difference in the momentum trend is likely due to the fact that hydrodynamic models typically have transverse momentum fluctuations that are larger than seen experimentally.
Année de publication : 2019
Revue : Phys. Rev. C 100 054905 (2019)
DOI : 10.1103/PhysRevC.100.054905
Preprint : arXiv:1906.03045
Langue : Anglais

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