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Lifetime of the magnetic field in heavy-ion collisions

Determine whether the magnetic field generated in off-central heavy-ion collisions is sufficiently long-lived to be treated as part of the equilibrated quark–gluon plasma, thereby justifying equilibrium-based descriptions of its effects on QCD matter.

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Background

In off-central heavy-ion collisions, strong electromagnetic fields are produced by spectator charges and may influence the evolution of the quark–gluon plasma. Whether these fields persist long enough to affect the equilibrated medium is crucial for interpreting experimental signatures (e.g., anomalous transport) within equilibrium or near-equilibrium frameworks.

The review highlights that the time dependence and spatial localization of these fields challenge their inclusion in equilibrium lattice-QCD predictions. Establishing their lifetime relative to thermalization and hydrodynamization timescales is therefore a central open issue with direct phenomenological impact.

References

To what extent the magnetic field is to be viewed as part of the equilibrated system, i.e. whether the magnetic field is sufficiently long-lived, is as of today, still one of the most important open questions of the field and the subject of ongoing debates.

— QCD with background electromagnetic fields on the lattice: a review (2406.19780 - Endrodi, 28 Jun 2024) in Section 1, Introduction