Chiral magnetic effect search in p+Au, d+Au and Au+Au collisions at RHIC

The chiral magnetic effect (CME) is a fundamental property of QCD. A major background source for CME measurements is the intrinsic particle correlations (such as resonances/jets decay) coupled with the azimuthal elliptical anisotropy $v_{2}$. In heavy-ion collisions, the magnetic field direction and event plane azimuthal angle $\Psi_{2}$ are correlated, thus the CME and the $v_{2}$-induced background are entangled. In small system p+Au and d+Au collisions, the $\Psi_{2}$ is mostly due to geometry fluctuations, and thus magnetic field direction and $\Psi_{2}$ are uncorrelated. The correlation measurements in small system collisions with respect to $\Psi_{2}$ are only sensitive to $v_{2}$-induced background while any CME is averaged to zero. In this talk, we will present the STAR measurements of two-particle correlations with respect to $\Psi_{2}$ in p+Au, d+Au and Au+Au collisions at $\sqrt{s_{\rm NN}}$ = 200 GeV. These results are analyzed as a function of particle multiplicity to shed light on the background contaminations of the CME measurements in heavy-ion collisions. We will also report results from a new analysis approach as a function of the particle pair invariant mass in order to suppress non-CME related physics backgrounds.