Particle production in strong electromagnetic fields in relativistic heavy-ion collisions

Abstract: I review the origin and properties of electromagnetic fields produced in heavy ion collisions. The field strength immediately after a collision is proportional to the collision energy and reaches eB\sim(m_\pi)^2 at RHIC and eB\sim10 (m_\pi)^2 at LHC. I demonstrate by explicit analytical calculation that after dropping by about one-two orders of magnitude during the first fm/c of plasma expansion, it freezes out and lasts for as long as quark-gluon plasma exists as a consequence of finite electrical conductivity of the plasma. Magnetic field breaks spherical symmetry in the direction perpendicular to the reaction plane and therefore all kinetic coefficients are anisotropic. I examine viscosity of QGP and show that magnetic field induces azimuthal anisotropy on plasma flow even in spherically symmetric geometry. Very strong electromagnetic field has an important impact on particle production. I discuss the problem of energy loss and polarization of fast fermions due to synchrotron radiation, consider photon decay induced by magnetic field, elucidate J/Psi dissociation via Lorentz ionization mechanism and examine electromagnetic radiation by plasma. I conclude that all processes in QGP are affected by strong electromagnetic field and call for experimental investigation.

• The paper demonstrates that electromagnetic fields, initially scaling with collision energy, stabilize in the quark-gluon plasma due to its finite electrical conductivity.
• The paper shows that magnetic fields break spherical symmetry in the quark-gluon plasma, leading to anisotropic kinetic properties and flow patterns.
• The paper highlights that strong electromagnetic fields enhance particle production through mechanisms like synchrotron radiation, photon decay, and quarkonium dissociation.

Overview of "Particle production in strong electromagnetic fields in relativistic heavy-ion collisions"

The paper authored by Kirill Tuchin presents a comprehensive examination of the interplay between strong electromagnetic fields and particle production during relativistic heavy-ion collisions, with particular focus on phenomena at facilities such as the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC). This study elucidates the dynamics of quark-gluon plasma (QGP) and explores its response to extreme electromagnetic conditions.

Key Findings and Methodologies

1. Electromagnetic Field Dynamics: The work reviews the origin and evolution of electromagnetic fields generated in heavy-ion collisions. The initial field strength scales with the collision energy, reaching approximately $m_\pi^2$ at RHIC and $10 m_\pi^2$ at LHC. It is shown via analytical solutions that after an initial decline, the fields stabilize due to the plasma's finite electrical conductivity, persisting throughout the plasma's lifespan.
2. Anisotropy Induced by Magnetic Fields: The paper explores how magnetic fields induce anisotropic behavior in QGP. Magnetic fields break the spherical symmetry in directions perpendicular to the reaction plane, leading to anisotropy in kinetic coefficients like viscosity. This symmetry breaking results in an azimuthal anisotropy in plasma flow, even under spherically symmetric initial conditions.
3. Impact on Particle Production: Strong electromagnetic fields significantly affect particle production. The study explores several processes:
   • Synchrotron Radiation: Fast quarks lose energy through synchrotron radiation in magnetic fields, contributing to energy loss mechanisms in QGP.
   • Photon Decay: Magnetic fields can induce photon decay processes, leading to additional particle production channels.
   • Quarkonium Dissociation: Mechanisms such as Lorentz ionization are discussed, wherein quarkonium states are dissociated by electromagnetic fields, influencing observable yields in experiments.
   • Polarization Effects: The paper also considers the polarization of particles, such as fast fermions, due to synchrotron radiation, and suggests experimental searches for these phenomena.

Implications and Future Directions

The research carries significant implications for theoretical and experimental studies of QGP. Understanding how electromagnetic fields influence QGP dynamics can help unravel finer details about the strong interaction and the early universe conditions recreated in collider experiments. The adaptations of classical electrodynamics observed at critical field strengths could provide avenues for exploring novel quantum electrodynamic effects in extreme conditions.

Experimentally, the findings emphasize the need for measuring electromagnetic effects on particle yields and anisotropic flows in heavy-ion collision data. The work posits several observables, like particle spectra and polarization signatures, which could validate theoretical predictions and refine our understanding of QGP properties.

In conclusion, the investigation brings to light the crucial role of electromagnetic fields in shaping the phenomenology of heavy-ion collisions. Advancements in experimental techniques to capture these subtle effects, alongside more refined theoretical models incorporating these dynamics, could significantly enrich our comprehension of fundamental physics at extreme conditions.