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Constraints on the chiral magnetic effect using charge-dependent azimuthal correlations in p Pb and PbPb collisions at the CERN Large Hadron Collider

Constraints on the chiral magnetic effect using charge-dependent azimuthal correlations in p Pb and PbPb collisions at the CERN Large Hadron Collider
Constraints on the chiral magnetic effect using charge-dependent azimuthal correlations in p Pb and PbPb collisions at the CERN Large Hadron Collider
Charge-dependent azimuthal correlations of same- and opposite-sign pairs with respect to the second- and third-order event planes have been measured in pPb collisions at √sNN=8.16TeV and PbPbcollisions at 5.02 TeV with the CMS experiment at the LHC. The measurement is motivated by the search for the charge separation phenomenon predicted by the chiral magnetic effect (CME) in heavy ion collisions. Three- and two-particle azimuthal correlators are extracted as functions of the pseudorapidity difference, the transverse momentum (pT) difference, and the pT average of same- and opposite-charge pairs in various event multiplicity ranges. The data suggest that the charge-dependent three-particle correlators with respect to the second- and third-order event planes share a common origin, predominantly arising from charge-dependent two-particle azimuthal correlations coupled with an anisotropic flow. The CME is expected to lead to a v2-independent three-particle correlation when the magnetic field is fixed. Using an event shape engineering technique, upper limits on the v2-independent fraction of the three-particle correlator are estimated to be 13% for pPb and 7% for PbPbcollisions at 95% confidence level. The results of this analysis, both the dominance of two-particle correlations as a source of the three-particle results and the similarities seen between PbPb and pPb, provide stringent constraints on the origin of charge-dependent three-particle azimuthal correlations and challenge their interpretation as arising from a chiral magnetic effect in heavy ion collisions.
0556-2813
Belyaev, Alexander
6bdb9638-5ff9-4b65-a8f2-34bae3ac34b3
The CMS Collaboration
Belyaev, Alexander
6bdb9638-5ff9-4b65-a8f2-34bae3ac34b3

Belyaev, Alexander , The CMS Collaboration (2018) Constraints on the chiral magnetic effect using charge-dependent azimuthal correlations in p Pb and PbPb collisions at the CERN Large Hadron Collider. Physical Review C, 97, [044912]. (doi:10.1103/PhysRevC.97.044912).

Record type: Article

Abstract

Charge-dependent azimuthal correlations of same- and opposite-sign pairs with respect to the second- and third-order event planes have been measured in pPb collisions at √sNN=8.16TeV and PbPbcollisions at 5.02 TeV with the CMS experiment at the LHC. The measurement is motivated by the search for the charge separation phenomenon predicted by the chiral magnetic effect (CME) in heavy ion collisions. Three- and two-particle azimuthal correlators are extracted as functions of the pseudorapidity difference, the transverse momentum (pT) difference, and the pT average of same- and opposite-charge pairs in various event multiplicity ranges. The data suggest that the charge-dependent three-particle correlators with respect to the second- and third-order event planes share a common origin, predominantly arising from charge-dependent two-particle azimuthal correlations coupled with an anisotropic flow. The CME is expected to lead to a v2-independent three-particle correlation when the magnetic field is fixed. Using an event shape engineering technique, upper limits on the v2-independent fraction of the three-particle correlator are estimated to be 13% for pPb and 7% for PbPbcollisions at 95% confidence level. The results of this analysis, both the dominance of two-particle correlations as a source of the three-particle results and the similarities seen between PbPb and pPb, provide stringent constraints on the origin of charge-dependent three-particle azimuthal correlations and challenge their interpretation as arising from a chiral magnetic effect in heavy ion collisions.

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PhysRevC.97.044912 - Version of Record
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e-pub ahead of print date: 23 April 2018

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Local EPrints ID: 421165
URI: http://eprints.soton.ac.uk/id/eprint/421165
ISSN: 0556-2813
PURE UUID: d0ddcdf0-63d4-485c-95b4-7873f214599b
ORCID for Alexander Belyaev: ORCID iD orcid.org/0000-0002-1733-4408

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Date deposited: 24 May 2018 16:30
Last modified: 17 Dec 2019 01:44

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