# Quark Matter 2018

13-19 May 2018
Venice, Italy
Europe/Zurich timezone
The organisers warmly thank all participants for such a lively QM2018! See you in China in 2019!

## An event-shape-engineering method to study charge separation in heavy-ion collisions

15 May 2018, 17:00
2h 40m
First floor and third floor (Palazzo del Casinò)

### First floor and third floor

#### Palazzo del Casinò

Poster Chirality, vorticity and polarisation effects

### Speaker

Dr Gang Wang (UCLA)

### Description

Recent measurements of charge-dependent azimuthal correlations in high-energy heavy-ion collisions at RHIC and the LHC have indicated charge-separation signals perpendicular to the reaction plane, and have been related to the chiral magnetic effect (CME) (see a review in Ref [1]). The discovery of this phenomenon in heavy-ion collisions will signify simultaneously three important physics ingredients: the strongest magnetic field ever made by mankind, the chirality imbalance caused by vacuum transition, and the chiral symmetry restoration in the deconfined nuclear matter. However, the correlation signal is contaminated with the background driven by the elliptic flow ($v_2$) of the collision system [2], and an effective approach is needed to remove the flow background from the correlation.

In this talk, we will disclose a few shortcomings of a previous attempt of the event shape engineering (ESE) based on the "event-by-event $v_2$" [3]. We will further present a novel ESE technique [4] utilizing the magnitude of the flow vector to select spherical events in heavy-ion collisions, which leaves the charge separation measurements free of flow contributions. The simplified Monte Carlo simulations and a multi-phase transport model (AMPT) are employed to develop the ESE scheme to reveal the true CME signals from the experimental observation. Caveats regarding artificial effects and extreme conditions in this method will also be discussed.

References
1. D.E. Kharzeev et al., Prog. Part. Nucl. Phys. 88 (2016) 1.
2. A. Bzdak et al., Phys. Rev. C 83 (2011) 014905 .
3. L. Adamczyk et al., [STAR Collaboration], Phys. Rev. C 89 (2014) 044908.
4. F. Wen et al., Chinese Phys. C 42(1) (2018) 014001 [arXiv:1608.03205].

Content type Theory Presenter name already specified

### Primary author

Mr Liwen Wen (University of California, Los Angeles)

### Co-authors

Dr Gang Wang (UCLA) Prof. Huan Huang (UCLA; Key Laboratory for Nuclear Physics and Ion-Beam Applications (MOE) and Institute of Modern Physics, Fudan University, Shanghai, China)