Symmetry Breaking in the Strong Interaction-The Chiral Magnetic Effect
The chiral magnetic effect(CME)refers to a charge separation along a strong magnetic field due to an imbalanced chirality of quarks from interactions with the vacuum topological gluon field.This chiral anomaly is a fundamental property of quantum chromodynamics(QCD)and,therefore,an observation of the CME would have far-reaching impact on our understanding of QCD and Nature.The measurements of the CME-sensitive azimuthal cor-relator Δγ observable in heavy-ion collisions are contaminated by a major background induced by elliptic flow aniso-tropy.Several novel approaches have been carried out,including a dedicated isobar collision program,to address this flow-induced background.Further background effects,arising from nonflow correlations,have been studied.While the isobar data are consistent with zero CME signal with an upper limit of 10％of the measured Δγ,the Au+Au mid-central data suggest a positive CME signal on the order of 10％of the measured Δγ with a significance of～2 stand-ard deviations.Future increased statistics and improved detector capability should yield a firm conclusion on the ex-istence(or the lack)of the CME in relativistic heavy-ion collisions.
chiral magnetic effectcharge separationΔγ correlatorflow-induced backgroundnonflow
NETL
NSTL
万方数据
