Measurements of multiparticle azimuthal correlations (cumulants) for charged particles in p-Pb at sNN=5.02 TeV and Pb-Pb at sNN=2.76 TeV collisions are presented. They help address the question of whether there is evidence for global, flowlike, 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 |Δη| 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 v24 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 v24≃v26≠0 which is indicative of a Bessel-Gaussian function for the v2 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 |Δη|>1.4 gap is placed. © 2014 CERN, for the ALICE Collaboration.

Multiparticle azimuthal correlations in p -Pb and Pb-Pb collisions at the CERN Large Hadron Collider / Abelev, B., Adam, J., Adamová, D., Aggarwal, M.M., Aglieri Rinella, G., Agnello, M., Agostinelli, A., Agrawal, N., Ahammed, Z., Ahmad, N., Ahmed, I., Ahn, S.U., Ahn, S.A., Aimo, I., Aiola, S., Ajaz, M., Akindinov, A., Alam, S.N., Aleksandrov, D., Alessandro, B., et al.. - In: PHYSICAL REVIEW. C, NUCLEAR PHYSICS. - ISSN 0556-2813. - 90:5(2014). [10.1103/PhysRevC.90.054901]

Multiparticle azimuthal correlations in p -Pb and Pb-Pb collisions at the CERN Large Hadron Collider

BRUNO, Giuseppe Eugenio;
2014

Abstract

Measurements of multiparticle azimuthal correlations (cumulants) for charged particles in p-Pb at sNN=5.02 TeV and Pb-Pb at sNN=2.76 TeV collisions are presented. They help address the question of whether there is evidence for global, flowlike, 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 |Δη| 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 v24 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 v24≃v26≠0 which is indicative of a Bessel-Gaussian function for the v2 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 |Δη|>1.4 gap is placed. © 2014 CERN, for the ALICE Collaboration.
2014
https://journals.aps.org/prc/abstract/10.1103/PhysRevC.90.054901
Multiparticle azimuthal correlations in p -Pb and Pb-Pb collisions at the CERN Large Hadron Collider / Abelev, B., Adam, J., Adamová, D., Aggarwal, M.M., Aglieri Rinella, G., Agnello, M., Agostinelli, A., Agrawal, N., Ahammed, Z., Ahmad, N., Ahmed, I., Ahn, S.U., Ahn, S.A., Aimo, I., Aiola, S., Ajaz, M., Akindinov, A., Alam, S.N., Aleksandrov, D., Alessandro, B., et al.. - In: PHYSICAL REVIEW. C, NUCLEAR PHYSICS. - ISSN 0556-2813. - 90:5(2014). [10.1103/PhysRevC.90.054901]
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11589/56993
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