Background study of the CME-related correlations in heavy-ion collisions within a multiphase transport mode

4 Nov 2019, 17:40
20m
Wanda Han Show Theatre & Wanda Reign Wuhan Hotel

Wanda Han Show Theatre & Wanda Reign Wuhan Hotel

Poster Presentation Chirality, vorticity and spin polarization Poster Session

Speakers

Dr Subikash Choudhury (Fudan University)Dr Wanbing He (Fudan University)

Description

The Chiral Magnetic Effect (CME) manifests itself via a separation of electric charge along the direction of the magnetic field, produced by spectator protons in heavy-ion collisions. The experimental searches for the CME, based on the charge-dependent angular correlations [1] have, however, remained inconclusive till date, because the observed features of charge separation in data are also compatible with non-CME background sources. Recently, the CMS collaboration attempted to disambiguate the origin of charge separation by measuring charge-dependent angular correlations or $\gamma$-correlators with respect to second-order ($\Psi_{2}$) and third-order ($\Psi_{3}$) symmetry planes defined as $\gamma_{112}$ and $\gamma_{123}$ respectively, in p+Pb and Pb+Pb collisions [2]. The idea is that an equality is expected in $\frac{\Delta\gamma_{112}}{\Delta\delta \times v_{2}}$ ($\kappa_{112}$) and $\frac{\Delta\gamma_{123}}{\Delta\delta \times v_{3}}$ ($\kappa_{123}$), if the charge separations are dominated by non-CME backgrounds \cite{CMS_3p}. The CMS measurements indeed reveal such equality across light-ion and heavy-ion collision systems, suggesting the observed charge separation in data arises from non-CME background contributions to a large extent. However, the signals and backgrounds in data are so entangled that such an interpretation may be naive. Instead, non-CME background models could provide a testing ground to verify or falsify such relations. In this poster, we will present results of different harmonics of $\gamma$-correlators calculated from a charge-conserved version of a multiphase transport (AMPT) model. In contrary to the CMS expectation, the AMPT model calculations show $(\kappa_{132} \approx 1) < (\kappa_{112} \approx 1.3) < (\kappa_{123} \approx 2)$.

References
[1] “Parity violation in hot QCD: how to detect it”, S. Voloshin, Phys. Rev. C70, 057901 (2004).
[2]“Constraints on the chiral magnetic effect using charge-dependent azimuthal correlations in pPb and PbPb collisions at the LHC, The CMS Collaboration”, Phys. Rev. C 97, 044912 (2018).

Primary authors

Dr Subikash Choudhury (Fudan University) Dr Wanbing He (Fudan University) Prof. Huan Zhong Huang (Fudan University/ UCLA) Dr Gang Wang (UCLA)

Presentation Materials

There are no materials yet.