# Multi-particle azimuthal correlations in p-Pb and Pb-Pb collisions at the CERN Large Hadron Collider

Abstract : Measurements of multi-particle azimuthal correlations (cumulants) for charged particles in p-Pb at $\sqrt{s_{\rm NN}} = 5.02$ TeV and Pb-Pb at $\sqrt{s_{\rm NN}} = 2.76$ TeV collisions are presented. They help address a question if there is evidence for global, flow-like, azimuthal correlations in the p-Pb system. Comparisons are made to measurements from the larger Pb-Pb system, where such evidence is established. In particular, the second harmonic two-particle cumulants are found to decrease with multiplicity, characteristic of a dominance of few-particle correlations in p-Pb collisions. However, when a $|\Delta \eta|$ gap is placed to suppress such correlations, the two-particle cumulants begin to rise at high-multiplicity, indicating the presence of global azimuthal correlations. The Pb-Pb values are higher than the p-Pb values at similar multiplicities. In both systems, the second harmonic four-particle cumulants exhibit a transition from positive to negative values when the multiplicity increases. The negative values allow for a measurement of $v_{2}\{4\}$ to be made, which is found to be higher in Pb-Pb collisions at similar multiplicities. The second harmonic six-particle cumulants are also found to be higher in Pb-Pb collisions. In Pb-Pb collisions, we generally find $v_{2}\{4\} \simeq v_{2}\{6\}\neq 0$ which is indicative of a Bessel-Gaussian function for the $v_{2}$ distribution. For very high-multiplicity Pb-Pb collisions, we observe that the four- and six-particle cumulants become consistent with 0. Finally, third harmonic two-particle cumulants in p-Pb and Pb-Pb are measured. These are found to be similar for overlapping multiplicities, when a $|\Delta\eta| > 1.4$ gap is placed.
Document type :
Journal articles

http://hal.in2p3.fr/in2p3-01003952
Contributor : Sylvie Flores Connect in order to contact the contributor
Submitted on : Wednesday, June 11, 2014 - 7:11:58 AM
Last modification on : Thursday, December 16, 2021 - 2:11:13 PM

### Citation

B. Abelev, Laurent Aphecetche, Guillaume Batigne, I. Belikov, C. Cheshkov, et al.. Multi-particle azimuthal correlations in p-Pb and Pb-Pb collisions at the CERN Large Hadron Collider. Physical Review C, American Physical Society, 2014, 90, pp.054901. ⟨10.1103/PhysRevC.90.054901⟩. ⟨in2p3-01003952⟩

### Metrics

Les métriques sont temporairement indisponibles