Background control and upper limit on the chiral magnetic effect in isobar collisions at √SNN = 200 GeV from STAR.

The STAR Collaboration has reported results from a blind analysis of isobar collisions (4496Ru + 4496Ru , 4096Zr + 4096Zr) at √SNN = 200 GeV on the search for the chiral magnetic effect (CME). Significant differences were observed in the measured multiplicity (N) and elliptic anisotropy (v2) between the two isobar systems. In these proceedings, we present two post-blind analyses aimed at mitigating remaining background effects. The first involves employing an event weighting procedure to match the distributions in N and v2 and then comparing the CME-sensitive Δγ correlator and signed balance functions. The second analysis investigates the contributions of the two- and three-particle nonflow to the isobar ratio of Δγ/v2. The estimated background baseline is consistent with the isobar measurements, and an upper limit is extracted on the CME signal. [ABSTRACT FROM AUTHOR]