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

Beam Energy and Collisions System Dependence of Charge Separation Relative to the Second-, Third- and Fourth-order Event Planes and the Implications for the Search for Chiral Magnetic Effects in STAR

May 15, 2018, 5:00 PM
2h 40m
First floor and third floor (Palazzo del Casinò)

First floor and third floor

Palazzo del Casinò

Poster Chirality, vorticity and polarisation effects Poster Session


Niseem Abdelrahman"Magdy" (Stony Brook University)


We present new differential measurements of charge separation relative to the second- ($\Psi_2$), third- ($\Psi_3$) and fourth-order ($\Psi_4$) event planes for Au+Au collisions at $\sqrt{s_{NN}}$= 200, 39, 27 and 19.6~GeV, U+U at $\sqrt{s_{NN}}$= 193 GeV and Cu+Au, Cu+Cu, d+Au and p+Au at $\sqrt{s_{NN}}$=200 GeV. The measurements are performed with a charge-sensitive correlator $R(\Delta S)$ [1] and the three-particle mixed harmonic correlator $\mathrm{C_{m,n,m+n} = \left< cos(m\phi_1 + n\phi_2 -(m+n)\phi_3)\right>}$ [2]. These are expected to give different responses to the CME-driven charge separation and non-CME background correlations. The $R(\Delta S)$ measurements are found to be flat relative to $\Psi_3$ in all systems and $\Psi_2$ in p(d)+Au systems, consistent with the expectation of random $\vec{B}$-field orientations relative to these event planes. In contrast, the heavy-ion measurements relative to $\Psi_2$ show concave-shaped $R(\Delta S)$ distributions, which is consistent with the presence of CME-driven charge separation characterized by an out-of-plane Fourier dipole coefficient $a_1$. We will present and discuss $R(\Delta S)$ and $\mathrm{C_{m,n,m+n}}$ measurements for a broad range of transverse momenta, pseudorapidity, and centrality intervals and compare it with model predictions [1]. The implication of these measurements for the upcoming isobar collisions at RHIC will also be discussed.

[1] N. Magdy, S. Shi, J. Liao, N. Ajitanand, and R. A. Lacey, arXiv:1710.01717.
[2] L. Adamczyk et al. (STAR Collaboration), arXiv:1701.06496.

Centralised submission by Collaboration Presenter name already specified
Content type Experiment
Collaboration STAR

Primary author

Zhenyu Ye (University of Illinois at Chicago)

Presentation materials