PoS - Proceedings of Science
Volume 314 - The European Physical Society Conference on High Energy Physics (EPS-HEP2017) - Heavy Ion Physics (Parallel Session). Conveners: Ralf Averbeck; Raphael Granier de Cassagnac; Carlos Salgado. Scientific Secretary: Andrea Dainese.
Recent Results on Multi-Particle Azimuthal Correlations in High-Multiplicity pp and pPb Collisions in CMS
C.A. Bernardes*  on behalf of the CMS Collaboration
Full text: pdf
Pre-published on: October 19, 2017
Published on: March 20, 2018
Abstract
In nucleus-nucleus collisions, the Quark-Gluon Plasma behaves like a perfect fluid and
the azimuthal anisotropy of the observed particle final-state distributions reflects its properties.
This anisotropic flow, arising mainly from initial-state geometry and its fluctuations,
highlights the collective behavior of the particles produced in the collision.
It is well-described by hydrodynamics and explains the long-range near-side correlations, known as the ``ridge'',
observed experimentally in AA collisions and, more recently, in small systems such as pp or pA collisions.
The CMS experiment has studied this correlation in details by extracting the momenta of the Fourier decomposition of azimuthal
particle-distribution in the final state ($v_\mathrm{n}$, n = 2 - 4). The $v_\mathrm{n}$ are extracted using di-hadron correlation
and multi-particle cumulant methods in both pp and pPb collisions. In this talk, results from CMS on the ridge in small systems
are shown and compared with those in PbPb collisions, demonstrating that the collective nature of the ridge
is present also in small systems. The correlation between different Fourier coefficients is further
investigated using a symmetric cumulant analysis and compared across colliding systems.
The latest results on $v_\mathrm{n}$ correlations in pp at 13 TeV and pPb at 8.16 TeV collisions are also discussed.
All these results give us a better understanding of collective effects from small to large
colliding systems and provide more insights on the nature of the ridge in pp and pPb collisions.
DOI: https://doi.org/10.22323/1.314.0155
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