Measurements of multiparticle azimuthal correlations (cumulants) for charged particles in p-Pb at root s(NN) = 5.02 TeV and Pb-Pb at root s(NN) = 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 vertical bar Delta eta vertical bar 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} similar or equal to v(2){6} not equal 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 vertical bar Delta eta vertical bar > 1.4 gap is placed.

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

Cicalo C.;DE FALCO, ALESSANDRO;Fionda F. M.;PUDDU, GIOVANNA;SIDDHANTA, SABYASACHI;USAI, GIANLUCA;
2014-01-01

Abstract

Measurements of multiparticle azimuthal correlations (cumulants) for charged particles in p-Pb at root s(NN) = 5.02 TeV and Pb-Pb at root s(NN) = 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 vertical bar Delta eta vertical bar 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} similar or equal to v(2){6} not equal 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 vertical bar Delta eta vertical bar > 1.4 gap is placed.
File in questo prodotto:
Non ci sono file associati a questo prodotto.

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11584/96467
 Attenzione

Attenzione! I dati visualizzati non sono stati sottoposti a validazione da parte dell'ateneo

Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus 186
  • ???jsp.display-item.citation.isi??? 157
social impact