Constraints on the chiral magnetic effect using charge-dependent azimuthal correlations in pPb 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 thirdorder event planes have been measured in pPb collisions at √sNN = 8.16 TeV and PbPb collisions at 5.02 TeV with the CMS experiment at the LHC. The measurement is motivated by the search fo...
| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English English English |
| Published: |
American Physical Society
2018
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| Subjects: | |
| Online Access: | http://irep.iium.edu.my/65494/ http://irep.iium.edu.my/65494/ http://irep.iium.edu.my/65494/ http://irep.iium.edu.my/65494/1/65494_Constraints%20on%20the%20chiral%20magnetic%20effect_article.pdf http://irep.iium.edu.my/65494/2/65494_Constraints%20on%20the%20chiral%20magnetic%20effect_scopus.pdf http://irep.iium.edu.my/65494/13/65494_Constraints%20on%20the%20chiral%20magnetic%20effect%20using%20charge-dependent%20azimuthal%20correlations%20in%20pPb%20and%20PbPb%20collisions%20at%20the%20CERN%20Large%20Hadron%20Collider_WOS.pdf |
| Summary: | Charge-dependent azimuthal correlations of same- and opposite-sign pairs with respect to the second- and thirdorder
event planes have been measured in pPb collisions at √sNN = 8.16 TeV and PbPb collisions 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 PbPb collisions 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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