New experimental constrains on chiral magnetic effect using charge-dependent azimuthal correlation in pPb and PbPb collisions at the LHC

Zhoudunming Tu,A Ayala Mercado,E Cuautle Flores

doi:10.1051/epjconf/201817201004

Zhoudunming Tu, A Ayala Mercado + Show 1 more

Open Access

https://doi.org/10.1051/epjconf/201817201004

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Abstract

Studies of charge-dependent azimuthal correlations for the same- and oppositesign particle pairs are presented in PbPb collisions at 5 TeV and pPb collisions at 5 and 8.16 TeV, with the CMS experiment at the LHC. The azimuthal correlations are evaluated with respect to the second- and also higher-order event planes, as a function of particle pseudorapidity and transverse momentum, and event multiplicity. By employing an event-shape engineering technique, the dependence of correlations on azimuthal anisotropy flow is investigated. Results presented provide new insights to the origin of observed charge-dependent azimuthal correlations, and have important implications to the search for the chiral magnetic effect in heavy ion collisions.

Highlights

In relativistic heavy ion collisions, the metastable gluon field with nontrivial topological configurations may form, which can cause parity and charge conjugation parity violating effects [1,2,3,4]
One of the proposed background mechanisms is related to the local charge conservation coupled with an anisotropic flow at the freezeout surface, where short-range correlation caused by jets or resonance decays that coupled with a strong elliptic flow can play an important role in the charge-dependent three-particle correlator, γ [10,11,12]
The background mechanism has been explored, an upper limit on the v2-independent component fraction with respect to the γ112 correlator that is directly related to the chiral magnetic effect" (CME), has been set for both pPb and PbPb collisions using an event shape engineering (ESE) method

Summary

Introduction

In relativistic heavy ion collisions, the metastable gluon field with nontrivial topological configurations may form, which can cause parity and charge conjugation parity violating effects [1,2,3,4]. The very recent analysis done by the CMS Collaboration has developed a new experimental approach to study the background correlation, together with an upper limit for the CME signal using an event shape engineering (ESE) technique at LHC energies.

Results

Conclusion