Magnetic field induced hair structure in charmonium gluon-dissociation

TL;DR

This study investigates how external magnetic fields influence the gluon-dissociation of charmonium in quark-gluon plasma, revealing significant effects on dissociation cross-sections and wave functions, especially under strong magnetic fields.

Contribution

It introduces a QCD-based approach to analyze magnetic field effects on charmonium dissociation, including deformation and Landau level effects, which were not previously considered.

Findings

Magnetic fields significantly enhance gluon dissociation cross-sections.

Electric dipole transitions are notably affected for P-wave states.

Strong magnetic fields (eB=5 m_pi^2) induce measurable changes in high-energy nuclear collisions.

Abstract

We study electromagnetic field effect on charmonium gluon-dissociation in quark-gluon plasma. With the effective Hamiltonian derived from QCD multipole expansion under an external electromagnetic field, we first solve the two-body Schr\"odinger equation for a pair of charm quarks with mean field potentials for color and electromagnetic interactions and obtain the charmonium binding energies and wave functions, and then calculate the gluon-dissociation cross-section and decay width by taking the color electric and magnetic dipole interactions as perturbations above the mean field and employing Fermi's Golden Rule. Considering the charmonium deformation in magnetic field, the discrete Landau energy levels make the dissociation cross-section grow hair, and the electric dipole channel is significantly changed, especially for the $P-$wave states $\chi_{c0}$ and $\chi_{c\pm}$. From our numerical calculation, the magnetic field strength $eB=5~m_\pi^2$ already changes the gluon dissociation strongly, which may indicate measurable effects in high-energy nuclear collisions.