Chiral magnetic effect in nuclear collisions

When atomic nuclei collide at high speed, do they briefly produce a current that sends positive and negative charges in opposite directions along a magnetic field? The proposed cause is a quantum property of the hot quark matter they create.[1] [2]

Colliding nuclei produce hot matter and a strong, brief magnetic field. Do positive and negative charges separate along it because of a quantum imbalance, or are the measured particle patterns ordinary backgrounds? In the proposed chiral magnetic effect, changing gluon-field configurations create an imbalance between left- and right-chiral quark states—a chirality imbalance—which can drive a current. Experiments measure correlations among outgoing charged particles rather than that current directly.[1] [2]

Some lower-energy collisions show residual charge separation; other measurements find no significant signal. But positive and negative particles created together can remain correlated as the collision debris expands, without this quantum effect.[1] [2]

Flow suppression leaves energy-specific STAR residuals and ALICE upper limits. Local charge conservation and the published photon-nuclear calculation supply non-CME contributions; residual correlation alone is insufficient.[1] [2] [3]

Ordinary matter keeps quarks bound inside particles such as protons. Hot collisions test their behavior in a different state, including whether an imbalance between quantum states can produce a measurable current.[2]

The proposed current links changes in the strong force’s field configurations to bulk electric transport. Testing that link would show how a microscopic quantum law manifests in a rapidly expanding many-particle state, where conventional motion can obscure it.[1] [2]