Revisit the chiral magnetic effect expectation in isobaric collisions at the relativistic heavy ion collider

Isobaric Ru-96(44)+Ru-96(44) and Zr-96(40)+Zr-96(40) collisions at root S-NN = 200 GeV have been conducted at the Relativistic Heavy Ion Collider to circumvent the large flow-induced background in searching for the chiral magnetic effect (CME), predicted by the topological feature of quantum chromodynamics (QCD). Considering that the background in isobar collisions is approximately twice that in Au+Au collisions (due to the smaller multiplicity) and the CME signal is approximately half (due to the weaker magnetic field), we caution that the CME may not be detectable with the collected isobar data statistics, within similar to 2 sigma significance, if the axial charge per entropy density (n(5)/s) and the QCD vacuum transition probability are system independent. This expectation is generally verified by the Anomalous-Viscous Fluid Dynamics (AVFD) model. While our estimate provides an approximate experimental baseline, theoretical uncertainties on the CME remain large. (C) 2021 The Authors. Published by Elsevier B.V.

Automated summary

Isobaric collisions of Ru-96(44)+Ru-96(44) and Zr-96(40)+Zr-96(40) at root S-NN = 200 GeV were conducted to study the chiral magnetic effect (CME). Due to the large background and weaker signal in isobar collisions compared to Au+Au collisions, detecting the CME with the current data statistics may be challenging. The Anomalous-Viscous Fluid Dynamics (AVFD) model generally supports this expectation, but theoretical uncertainties on the CME still remain significant.